feat(build): add cleanup-markdown feature flag

[nylonicious]

Closes #1073

I also documented the feature flags.

[LucioFranco]

Thanks!

[LucioFranco]

Looks like we just have a CI failure that needs to be resolved before we can merge

[nylonicious]

All tests run fine on my local machine, so I'm not sure what's the issue. I've rebased but CI need approval.

[LucioFranco]

Ah @nylonicious since this changes the output of the generated code for tonic-types you will need to run cargo test --all then commit the extra code that was updated. That is why CI is failing.

[nylonicious]

I see, my bad. It now passes cargo test --all --all-features locally.