Rework automated version bumps

[tooomm]

Fixes #220

The script and comparison logic is kept unchanged, but the workflow around changed.

Pushes a new version to master branch for each change to the tokens.xml file on the same.
The workflow only runs for pushes that are not created by itself by checking the commit message to prevent loops.
Using a concurrency group should ensure to bump the version for each change still, even if they are queued due to several merges.

[tooomm]

@ebbit1q FYI

This works like a charm when merging PR's, or pushing to master directly.
Within a few secs after the commit, a version bump happens automatically.
No more manual version bumps needed!

[ebbit1q]

I considered this option in the past but found it to be suboptimal as it means all of these extra commits get made instead of squashing them into one, however my idea of having the bot push to the pr branch on review didn't always work because of permissions (the bot only is allowed access to the repo it's on) my alternative would be to make the workflow update and merge but it is more complicated and I never got around to it.

[tooomm]

I don't think this is a real issue.
If we have to evaluate comfort & robustness vs. avoiding some extra commits, I'm very much in favor of the first.

If you want to build an even better solution, sure!
For now, this is a simple way that always works (also for changes from external branches/forks).