Create workflow to label PRs needing rebase

[queengooborg]

This PR adds a GitHub Actions workflow to automatically (un)label pull requests that have merge conflicts. Fixes #5154.

[Rumyra]

This looks good to me 👍 making @schalkneethling aware of it in case we want something similar on other repos in the future (maybe not rebase, but something)

[schalkneethling]

This would actually be useful on Yari at the very least. @queengooborg, do you want to open a PR on mdn/workflows to this as a reusable action?

[queengooborg]

I opened mdn/workflows#33 which adds the workflow to our reusable workflows. I'd be happy to rework this PR to use the global workflow if/when it's merged!

[schalkneethling]

I opened mdn/workflows#33 which adds the workflow to our reusable workflows. I'd be happy to rework this PR to use the global workflow if/when it's merged!

Thank you! Just reviewed your pull request.

[Rumyra]

From what I can tell this is using the mdn/workflows one now - are we good to go?

[queengooborg]

Yep, we're all good to go!

[schalkneethling]

@queengooborg are we waiting on @foolip as well to 👍 ? If not, feel free to merge.

[queengooborg]

Only one owner needs to r+ on PRs to merge infra changes like this, so either Philip, Ruth or Florian (I can't approve my own PRs, sadly :P) is needed to approve and then we can merge!