CI: Add bot to track deprecation prs
We tend to forget to register deprecation prs in our deprecation log. This bot aims to solve this. Every time a PR with the label Deprecate is merged, it adds a new entry to the deprecation log.

In a future version I'd like to add the option to also check enforced deprecations automatically.

One TODO is how to handle PRs where we enforce deprecations:
- We could create a new label that does not affect the bot
- Add a switch to the bot when we start enforcing deprecations

We could get race conditions in theory, but it is not very likely, so would address if it becomes a problem.

Tried this in my repo and worked reliably

Pinging everyone who is regularly merging prs, hope I did not forget anyone
i don't know enough about GH workflows to comment on the implementation, but the idea sounds really neat +1 for trying this out. Nice, on board with the idea

I'm no security expert, but I guess there's no way for this to be exploited to get the secrets out of it? I don’t think so, I am basically using the same technique as our assign bot. 

Also, it’s not possible to trigger the bot again after the pr is merged I'll merge this, we can always revert if we get any problems. I have a deprecation pr ready that can test the bot