Add Github App for the devrel reviews and approvals workflow

[devnook]

App currently deployed at https://glitch.com/edit/#!/ash-wonderful-raja

Example repo with the app installed: https://github.com/devnook/developer.chrome.com/
Example config file: https://github.com/devnook/developer.chrome.com/blob/main/.github/chrome-devrel-bot.yml
Example PR: https://github.com/devnook/developer.chrome.com/pull/3

[jeffposnick]

Thanks for putting this together! None of these comments are huge issues, so I think we'll be able to go forward with this approach in general!

[devnook]

PTAL

[jeffposnick]

Just a few optional comments—this PR is mergeable as-is, so feel free to do that if you want to get the system set up sooner rather than later. You can address the feedback in follow-up PRs or just ignore it.

[jeffposnick]

I think the idea is that the non-200 responses show up with the error in the body in a GitHub Actions dashboard, based on the info in that blog post. So it could help with debugging even though Glitch doesn't expose the logs.

But I've never tried that out, and we don't need to block the PR on that.