Pull requests are just extended issues. I guess it is already possible: https://help.github.com/en/github/automating-your-workflow-with-github-actions/events-that-trigger-w...
on: issues: types: [milestoned]
I gave this a shot and it didn't work. Issues also has different metadata than pull_request so it wouldn't of worked for what I am doing.
Hey @spenrose, You are correct `milestoned` is not an activity type under the pull_request event as of now. I'll be sure to pass this feedback along to the team.
Mark helpful posts with Accept as Solution to help other users locate important info. Don't forget to give Kudos for great content!