Add CLI for generating IDL from Rust programs

[TanmayDhobale]

The problem #70

This adds codama-rs - a CLI tool that wraps the existing Codama::load() API to generate Codama IDL from Rust
programs:

# Generate to stdout
codama-rs generate-idl ./my-program

# Pretty print for debugging
codama-rs generate-idl ./my-program --pretty

# Save to file
codama-rs generate-idl ./my-program -o idl.json ```

allows users to use both codama-rs (to generate IDL) and codama (to perform actions from that IDL) side by side.

[lorisleiva]

Thank you so much for working on this. I've made a few small comments. Let me know what you think. 🙏

[lorisleiva]

Thank you! Just a small comment and LGTM.

Also do you mind adding codama-cli to the inputs.crate.options list in the .github/workflows/publish.yml workflow? I believe that's the crate registered everywhere after that.

EDIT: Ah and a quick lint fix.

[lorisleiva]

Thanks again for this! 🍺