ci: autoupdating translation stats via PRs

[RobPasMue]

This PR solves the autoupdating problem we currently have in the translation stats.
It will run once a month (or on demand) and it will trigger a PR to update the _static/translation_stats.json file in case any modification happened.

It leverages https://github.com/peter-evans/create-pull-request behind the scenes for the PR creation process.

Related to #493

[RobPasMue]

Not sure why the deploy workflow is not working @lwasser 😢

[sneakers-the-rat]

So I am not sure why we don't just remove translation stats from being versioned and then compute them every time we build the docs? Seems like they should be pretty cheap to compute, should always reflect the current status, and they aren't used anywhere but the graph? Seems like riding up to a month behind and needing to add another ci action might be a lil complicated

[sneakers-the-rat]

here's how i would do that: RobPasMue#1

[RobPasMue]

Hi @sneakers-the-rat! Sure, we can move to a single-process file generation. I'm fine with that option as well. Like I mentioned in #511 (comment) I went with my initial ideal which was to set up the workflow mechanism but I'm fine going with your approach as well. I think both of them are valid anyway, both of them have pros and cons - your case generates all in the fly and avoids making the file persistent, which is fine. But during discussions happening at the PyCon sprint with @lwasser I thought we would want it to persist. That's why I went with this approach. I know my approach has the downside of having "stale" information (until you run the workflow again manually or the scheduled run gets triggered).