feat: Autogeneration of the CLI documentation.

[ruben-arts]

Why?

Decrease future maintainance of the documentation, making sure it's always in sync with the tool.

How?

This PR introduces another Rust binary called pixi_docs which can be executed.
As a result it will create all the CLI docs for the pixi commands.
These will be put in the docs/autogenerated folder.

Updating the documentation can be done manually in two ways.

• Update the information wrapped in the clap commands in src/cli/<COMMAND>.rs
• Add extra information with the injection through snippets. Documentation about this can be found in docs/reference/cli/README.md

This generation is fully based on the clap::Command, which is really cool options of the clap parser!

TODO

To get this MVP in we should have moved all current documentation over, making sure we're not missing example from the original docs/reference/cli.md.

• Replace old documentation
• Push generated docs into the repo
• Create a CI stage that checks the generation

Out of scope of this PR

• We're not extending the documentation
• We're not adding groups to the options, this would make it easier to read the options for tools like pixi add
• We're not focusing on improving the docstrings in the documentation, unless they are wrong.

[Hofer-Julian]

Things that I noticed:

• Website title is concatenated without spaces: e.g. pixiglobaluninstall
• Many examples have broken lists: e.g. pixi global add
• Options are not rendered as lists, they just have a - in front
• Global & co should be a header in front of the option list instead of a prefix for each list element
• If you look at pixi init, you'll find that flag parameters are sometimes lowercase --channel (-c) channel and sometimes uppercase --import (-i) ENV_FILE

[Hofer-Julian]

Great work.

Would be nice to have a bit better reporting

[Hofer-Julian]

Awesome improvement! 📖