specs: auto generate table of contents (#1441)

## Motivation 
The table of contents at the top of each file can be a maintenance
burden. We can auto-generate it with
[mdbook-toc](https://github.com/badboy/mdbook-toc).

## Screenshot

Before | After
--- | ---
<img width="500" alt="before"
src="https://user-images.githubusercontent.com/3699047/222535783-8ad53ec3-43db-4e4b-ad8f-ea974061190b.png">
| <img width="479" alt="after"
src="https://user-images.githubusercontent.com/3699047/222535796-39c4172d-79b9-4e64-a492-7a68c37f5381.png">

specs/README.md

@@ -2,7 +2,12 @@
 
 ## Building From Source
 
-Prerequisite: [install mdBook](https://rust-lang.github.io/mdBook/guide/installation.html).
+Install [mdbook](https://rust-lang.github.io/mdBook/guide/installation.html) and [mdbook-toc](https://github.com/badboy/mdbook-toc):
+
+```sh
+cargo install mdbook
+cargo install mdbook-toc
+```
 
 To build book:
 

specs/book.toml

@@ -10,3 +10,7 @@ git-repository-url = "https://github.com/celestiaorg/celestia-app"
 
 [rust]
 edition = "2021"
+
+[preprocessor.toc]
+command = "mdbook-toc"
+renderer = ["html"]

specs/src/rationale/message_block_layout.md

@@ -1,9 +1,6 @@
 # Message Layout
 
-- [Preamble](#preamble)
-- [Message Layout Rationale](#message-layout-rationale)
-  - [Non-Interactive Default Rules](#non-interactive-default-rules)
-  - [Caveats](#caveats)
+<!-- toc -->
 
 ## Preamble
 

specs/src/specs/block_proposer.md

@@ -1,7 +1,6 @@
 # Honest Block Proposer
 
-- [Deciding on a Block Size](#deciding-on-a-block-size)
-- [Laying out Transactions and Messages](#laying-out-transactions-and-messages)
+<!-- toc -->
 
 This document describes the tasks of an honest block proposer to assemble a new block. Performing these actions is not enforced by the [consensus rules](./consensus.md), so long as a valid block is produced.
 

specs/src/specs/consensus.md

@@ -1,34 +1,6 @@
 # Consensus Rules
 
-- [System Parameters](#system-parameters)
-  - [Units](#units)
-  - [Constants](#constants)
-  - [Reserved Namespace IDs](#reserved-namespace-ids)
-  - [Reserved State Subtree IDs](#reserved-state-subtree-ids)
-  - [Rewards and Penalties](#rewards-and-penalties)
-- [Leader Selection](#leader-selection)
-- [Fork Choice](#fork-choice)
-- [Block Validity](#block-validity)
-- [Block Structure](#block-structure)
-  - [`block.header`](#blockheader)
-  - [`block.availableDataHeader`](#blockavailabledataheader)
-  - [`block.lastCommit`](#blocklastcommit)
-  - [`block.availableData`](#blockavailabledata)
-- [State Transitions](#state-transitions)
-  - [`block.availableData.transactionData`](#blockavailabledatatransactiondata)
-    - [SignedTransactionDataTransfer](#signedtransactiondatatransfer)
-    - [SignedTransactionDataMsgPayForData](#signedtransactiondatamsgpayfordata)
-    - [SignedTransactionDataCreateValidator](#signedtransactiondatacreatevalidator)
-    - [SignedTransactionDataBeginUnbondingValidator](#signedtransactiondatabeginunbondingvalidator)
-    - [SignedTransactionDataUnbondValidator](#signedtransactiondataunbondvalidator)
-    - [SignedTransactionDataCreateDelegation](#signedtransactiondatacreatedelegation)
-    - [SignedTransactionDataBeginUnbondingDelegation](#signedtransactiondatabeginunbondingdelegation)
-    - [SignedTransactionDataUnbondDelegation](#signedtransactiondataunbonddelegation)
-    - [SignedTransactionDataBurn](#signedtransactiondataburn)
-    - [SignedTransactionRedelegateCommission](#signedtransactionredelegatecommission)
-    - [SignedTransactionRedelegateReward](#signedtransactionredelegatereward)
-    - [Begin Block](#begin-block)
-    - [End Block](#end-block)
+<!-- toc -->
 
 ## System Parameters
 

specs/src/specs/data_structures.md

@@ -1,77 +1,6 @@
 # Data Structures
 
-- [Data Structures Overview](#data-structures-overview)
-- [Type Aliases](#type-aliases)
-- [Blockchain Data Structures](#blockchain-data-structures)
-  - [Block](#block)
-  - [Header](#header)
-  - [AvailableDataHeader](#availabledataheader)
-  - [AvailableData](#availabledata)
-  - [Commit](#commit)
-  - [Timestamp](#timestamp)
-  - [HashDigest](#hashdigest)
-  - [TransactionFee](#transactionfee)
-  - [Address](#address)
-  - [CommitSig](#commitsig)
-  - [Signature](#signature)
-- [ConsensusVersion](#consensusversion)
-- [Serialization](#serialization)
-- [Hashing](#hashing)
-- [Public-Key Cryptography](#public-key-cryptography)
-- [Merkle Trees](#merkle-trees)
-  - [Binary Merkle Tree](#binary-merkle-tree)
-    - [BinaryMerkleTreeInclusionProof](#binarymerkletreeinclusionproof)
-  - [Namespace Merkle Tree](#namespace-merkle-tree)
-    - [NamespaceMerkleTreeInclusionProof](#namespacemerkletreeinclusionproof)
-  - [Sparse Merkle Tree](#sparse-merkle-tree)
-    - [SparseMerkleTreeInclusionProof](#sparsemerkletreeinclusionproof)
-- [Erasure Coding](#erasure-coding)
-  - [Reed-Solomon Erasure Coding](#reed-solomon-erasure-coding)
-  - [2D Reed-Solomon Encoding Scheme](#2d-reed-solomon-encoding-scheme)
-  - [Share](#share)
-    - [Compact Share](#compact-share)
-    - [Sparse Share](#sparse-share)
-    - [Parity Share](#parity-share)
-    - [Namespace Padding Share](#namespace-padding-share)
-    - [Tail Padding Share](#tail-padding-share)
-  - [Arranging Available Data Into Shares](#arranging-available-data-into-shares)
-- [Available Data](#available-data)
-  - [TransactionData](#transactiondata)
-    - [WrappedTransaction](#wrappedtransaction)
-    - [Transaction](#transaction)
-    - [SignedTransactionData](#signedtransactiondata)
-      - [SignedTransactionDataTransfer](#signedtransactiondatatransfer)
-      - [SignedTransactionDataMsgPayForData](#signedtransactiondatamsgpayfordata)
-      - [SignedTransactionDataCreateValidator](#signedtransactiondatacreatevalidator)
-      - [SignedTransactionDataBeginUnbondingValidator](#signedtransactiondatabeginunbondingvalidator)
-      - [SignedTransactionDataUnbondValidator](#signedtransactiondataunbondvalidator)
-      - [SignedTransactionDataCreateDelegation](#signedtransactiondatacreatedelegation)
-      - [SignedTransactionDataBeginUnbondingDelegation](#signedtransactiondatabeginunbondingdelegation)
-      - [SignedTransactionDataUnbondDelegation](#signedtransactiondataunbonddelegation)
-      - [SignedTransactionDataBurn](#signedtransactiondataburn)
-      - [SignedTransactionRedelegateCommission](#signedtransactionredelegatecommission)
-      - [SignedTransactionRedelegateReward](#signedtransactionredelegatereward)
-  - [PayForBlobData](#payforblobdata)
-  - [IntermediateStateRootData](#intermediatestaterootdata)
-    - [WrappedIntermediateStateRoot](#wrappedintermediatestateroot)
-    - [IntermediateStateRoot](#intermediatestateroot)
-  - [MessageData](#messagedata)
-    - [Message](#message)
-- [State](#state)
-  - [StateElement](#stateelement)
-  - [Account](#account)
-  - [Delegation](#delegation)
-  - [Validator](#validator)
-  - [ActiveValidatorCount](#activevalidatorcount)
-  - [ActiveVotingPower](#activevotingpower)
-  - [ProposerBlockReward](#proposerblockreward)
-  - [ProposerInitialVotingPower](#proposerinitialvotingpower)
-  - [ValidatorQueueHead](#validatorqueuehead)
-  - [PeriodEntry](#periodentry)
-  - [Decimal](#decimal)
-  - [MessagePaid](#messagepaid)
-  - [MessagePaidHead](#messagepaidhead)
-- [Consensus Parameters](#consensus-parameters)
+<!-- toc -->
 
 ## Data Structures Overview
 

specs/src/specs/networking.md

@@ -1,15 +1,6 @@
 # Networking
 
-- [Wire Format](#wire-format)
-  - [AvailableData](#availabledata)
-  - [AvailableDataRow](#availabledatarow)
-  - [ConsensusProposal](#consensusproposal)
-  - [MsgWirePayForData](#msgwirepayfordata)
-- [Invalid Erasure Coding](#invalid-erasure-coding)
-  - [ShareProof](#shareproof)
-  - [BadEncodingFraudProof](#badencodingfraudproof)
-- [Invalid State Update](#invalid-state-update)
-  - [StateFraudProof](#statefraudproof)
+<!-- toc -->
 
 ## Wire Format