Added GitHub action to auto-assign issues

[paulooctavio]

Proposed changes

Added a GitHub Action to auto-assign an issue to a commenter when they comment "take". Fixes #204.

Types of changes

What types of changes does your code introduce to quinn?

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Further comments

The code was heavily inspired by the delta-rs code used as an example in the issue, with a few tweaks for readability.

[SemyonSinchenko]

@paulooctavio Sorry for a long answer and thank you for the contribution! May we test it? For example, can you merge this branch into your fork and we will try to create an issue in the fork and assign it?

[paulooctavio]

@SemyonSinchenko It's a pleasure to contribute! And I already did the testing and it worked.

[SemyonSinchenko]

Cool! Thanks again @paulooctavio! I left the only commentary