Generate manpages from tremor-cli clap definition

[mfelsche]

Describe the problem you are trying to solve

We lost our cli.yaml due to a clap upgrade. But we generated docs for our website from this yaml file. So we cannot generate any docs on our cli anymore. It would be nice to have this docs.

Describe the solution you'd like

With https://crates.io/crates/clap_mangen we have a crate that we could use to generate manpages. Those could be used to be rendered to markdown or HTML and be displayed on the website and they could also be packaged alongside with our release packages.

[AllMight2099]

Hey there!
I'd like to pick this issue up

[mfelsche]

@AllMight2099 hey, cool! One small concern though, we would need this rather soonish for the next release which is due soon. If you are fine with that extra pressure, i will assign this issue to you. As a strategy, rather make small iterative PRs or create a draft PR as soon as you have something, even if it is not yet quite working. We will provide feedback.

[AllMight2099]

Hey @mfelsche. I'd love to work on this. I ran an example of clap-mangen and I'm ready to integrate it with my fork and submit a PR. Tho, I do have one doubt. Are the docs already present (as markdown files) or do I have to generate the documentation from the cli into markdown/HTML?
Will you be free to discuss this on discord as I could get started right away 😃