Add GitHub issue template for deprecated APIs

[scottn12]

This PR adds a GitHub issue template for deprecated APIs. The issue will automatically have the "api deprecation" label applied, and have sections generated for the recommended information to include.

If this is merged, the API deprecation wiki doc should be updated to include use of this template.

[scottn12]

Is it possible to have it automatically assign the issue to the author? If so, we may want to consider that

[heliocliu]

Probably, right? If you're trying to encourage accountability of cleaning up deprecations. Otherwise in this sort of case it's kind of like throwing it into the void

[scottn12]

Yeah, I think that would be ideal, however I haven't been able to find anything documented on how to do that with templates. If it's not possible, I can just add a line to the template mentioning that it should be assigned to someone, and if you don't know who then assign yourself.

[tylerbutler]

Over the weekend I learned about a beta GitHub feature that might be a good fit here: https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/configuring-issue-templates-for-your-repository#creating-issue-forms.

I don't know if you can self-assign, though.

[scottn12]

I tested it out a little bit and it looks like you can't auto assign via issue templates and most likely not with issue forms either. However, I did find this GitHub Action that could work here. @tylerbutler what do you think?