Switch from Prolog to Erlang as backend and modify interface (#38)

Adds Erlang code generation and deletes corresponding Prolog code generation
Modifies interface to show terms top-to-bottom instead of bottom-to-top (so terms can only modify whatever is below them)
Updates documentation to correspond to these changes and the GitHub workflow to work properly

.github/workflows/release.yml

@@ -14,10 +14,13 @@ jobs:
             archive: zip
           - target: x86_64-unknown-linux-musl
             archive: tar.gz tar.xz
-          - target: x86_64-apple-darwin
-            archive: zip
+          #- target: x86_64-apple-darwin
+          #  archive: zip
     steps:
       - uses: actions/checkout@master
+      - uses: gleam-lang/setup-erlang@v1.1.3
+        with:
+          otp-version: "24.1"
       - name: Compile and release
         uses: rust-build/rust-build.action@latest
         env:

.gitignore

@@ -3,4 +3,5 @@ target/
 
 **/*.rs.bk
 
-.pdb
+.pdb
+mlatu.erl

CONTRIBUTING.md

@@ -8,7 +8,7 @@ Pull requests are very welcome. For major changes, please open an issue first to
 
 ## Setup
 
-To create a local copy of mlatu with all necessary dependencies, you will need to install Rust and Swi-Prolog. To install Rust, follow the instructions at <https://rustup.rs>. To install Swi-Prolog, you can find a download at <https://www.swi-prolog.org/Download.html>.
+To create a local copy of mlatu with all necessary dependencies, you will need to install Rust and Erlang. To install Rust, follow the instructions at <https://rustup.rs>. To install Erlang, you can find a download at <https://www.erlang.org/downloads>.
 
 To contribute to mlatu, it's easiest to install the GitHub CLI tool (instructions are at <https://github.com/cli/cli#installation>). After installation, authenticate yourself by running `gh auth login`. Then, fork and download a local copy of the repository by running `gh repo fork mlatu-lang/mlatu`.