Unit tests don't run in pull requests from forked repos

[jefflinse]

The unit test workflow is required for merging a pull request, but the action hangs when a pull request is opened from a fork.

[jtgrohn]

Can you fix this by checking the box in the image below?

A word of caution - I believe this will give PRs from forks access the repository secrets - so you want to be careful with this setting.