CLI: use hub's `create_commit`
# What does this PR do?

This PR changes the method to open PRs in `pt-to-tf` to the permanent method defined by the hub -- `create_commit`. It also updates the commit description (it now supports line breaks 🎉 ) and adds a flag to add extra description (so I can programmatically tag the right HF maintainer in certain repos)

We can see an example PR [here](https://huggingface.co/joaogante/test_text/discussions/9) -- @Rocketknight1 confirms that the notification got to him!

After this PR gets merged, we can announce `pt-to-tf`, as it no longer depends on unreleased functionality 🚀 
_The documentation is not available anymore as the PR was closed or merged._<|||||>Some CI runs have hub 0.7.0 cached, figuring how to best update it