Setup CI

[rsms]

Setup continuous integration on Github (using Actions) for compiling and testing font files on PRs and maybe even on every commit on master.

Some resources:

• https://help.github.com/en/github/automating-your-workflow-with-github-actions/about-github-actions
• https://help.github.com/en/github/automating-your-workflow-with-github-actions/configuring-a-workflow
• https://github.com/actions/starter-workflows/blob/master/ci/python-app.yml