Support for new stacked pull requests endpoints

[Not-Dhananjay-Mishra]

GitHub now have endpoints for Stacked Pull Requests.
docs - https://docs.github.com/en/rest/pulls/stacks?apiVersion=2022-11-28

[gmlewis]

Thank you, @Not-Dhananjay-Mishra - do you want to work on this, or shall we open this issue up to other contributors?

[Not-Dhananjay-Mishra]

Thank you, @Not-Dhananjay-Mishra - do you want to work on this, or shall we open this issue up to other contributors?

Let's open this issue for other contributors.

[gmlewis]

This would be a great PR for any new contributor to this repo or a new Go developer.
All contributions are greatly appreciated!

Feel free to volunteer for any issue and the issue can be assigned to you so that others don't attempt to duplicate the work.
Also feel free to perform a code review on any PR that has the label "NeedsReview" - we appreciate those contributions too!
We have a REVIEWERS file that you could add your username to if you are willing to be contacted when reviews are needed.

Please check out our CONTRIBUTING.md guide to get started. (In particular, please remember to go generate ./... and don't use force-push to your PRs.)

Thank you!

[Bortlesboat]

I'd like to work on this. I'll follow the existing service patterns, add endpoint coverage and fixtures, run generation, and post the PR once the implementation has been reviewed locally.

[gmlewis]

I'd like to work on this. I'll follow the existing service patterns, add endpoint coverage and fixtures, run generation, and post the PR once the implementation has been reviewed locally.

Thank you, @Bortlesboat! It's yours.