Add support for new pull request experience

[Peter Roth]

Observed behavior:

When using the (currently beta as of April 2019) new pull request experience the PR guidelines do not show up anywhere.

Expected behavior:

The PR guidelines are included/shown when using this new pull request experience.

[Ayush Sharma]

This is still a problem. This plug-in fixes a major oversight in the current BB experience, and we need this plugin to work in the new interface as well.

[Eilen Shahbaz]

This issue has been resolved and the feature should be available via the meatball menu directly to the right of the Merge button in the new pull request experience.

[Peter Roth]

I see it now! Excellent work, thanks so much!