feat: add fastify install command

[matthyk]

First draft for a new fastify-cli command called install. This command can be used for any existing Fastify project to browse and install Fastify core plugins. Usage is as follows:

• fastify install my-project: Launches an interactive CLI powered by Inquirer.js and the selected plugins will be installed in the folder my-project. A package.json must already exist in this folder.
• fastify install my-project --search sql: The CLI searches for any core plugin matching the given word and let the user select from the found plugins
• fastify help install shows:

Usage: fastify install <FOLDER>

Launches an interactive CLI application that allows you to browse and install Fastify plugins.
Requires an existing `package.json` file in the specified folder.

OPTS

  --search, -s
      search for plugins containing the given word

TODO's:

• Add tests
• update documentation
• Optimize search functionality

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[matthyk]

@mcollina Is this approach feasible? Some points that still need to be clarified for me:

• We have to use Inquirer version 8.x since later versions are ESM modules
• Currently, the versions of the plugins are controlled via the devDependencies in package.json. I am open to other/better approaches

[mcollina]

use the latest version and switch the CLI to esm, there is no real need for the CLI to be CJS.

[mcollina]

Tests are missing

[mcollina]

We should be downloading this from a public resource, and not duplicate the data here. Otherwise maintaining this would be problematic.

cc @Fdawgs @Eomm, where do you think it would be better to have this metadata? Could it be part of the website?