create action to check reprex

[maxheld83]

amazingly, someone build an action to parse reprexes from an issue, and check whether they work.

https://twitter.com/github/status/1159517303282835456

I'd like to build that for GitHub actions.

https://github.com/yarnpkg/berry?utm_campaign=1565285405&utm_medium=social&utm_source=twitter&utm_content=1565285405

This seems like a legit usage of actions in GitHub actions