Auto-apply T: based on commit prefixes

[perryprog]

Would be neat if 'T: Bugfix' could be applied if any commits in the PR had 'fix' as a prefix. Could then do similar for 'feat' and 'chore'.

To avoid being messy maybe it only does it on the initial PR creation since I often push 'fix' commits that are fixing an issue local to the PR, and that doesn't necessarily imply the PR itself is a bugfix. (Or it just uses the first commit which is probably "good enough" since it'll still need to be triaged.)

[Simyon264]

That sounds like a good idea.

[Fildrance]

According with https://www.conventionalcommits.org/en/v1.0.0 comits can have 'fix' within any PR if they fix certain problem. But we could do it if PR name contains prefix, or by parsing comment description (cl part). Sounds good.