Add GitHub action to test PRs

[hlascelles]

Recently PRs have made it in with malformed files: #236

Would you be open to adding a GitHub action to this repo to run make test?

[ppeble]

Oh yes, definitely. I am very much soured on Travis CI. I want it gone. I would gladly accept any help on that front!

[hlascelles]

Here's a kickstart. #239

Once merged you will have to enable it in the GitHub UI: https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/enabling-features-for-your-repository/managing-github-actions-settings-for-a-repository

I believe it will work, but not sure for certain until merged and enabled on your repo. 👍