Set up automated testing with CI

[jwflory]

In the past, we had a degree of automatic testing of changes with CircleCI. It was disabled because of missing documentation from a past contribution. It would be nice to set something back up again to ensure the site always successfully on each new pull request. I wonder if TravisCI would be more straightforward for the job.

[Tjzabel]

Now that the old CI has been removed from this project, it is time to figure out what we want to do for CI.

Some options that come to mind are using TravisCI, or potentially looking at GitHub Actions and the new GitHub CI.

[jrtechs]

Something like this might be good:
https://github.com/felixrieseberg/travis-jekyll-git

I like this solution in particular since it allows us to make sure that all the images and links works. This is particularly useful since it would let us know if adding/removing content breaks other pages on the website.

[Tjzabel]

Hmm...

We may be able to make use of something like that. We don't need any of the CD stuff there, but I do like the idea of being able to test links/images.

[MoralCode]

it seems like some kind of automated jekyll testing is in place on the fossrit site as noted in FOSSRIT/fossrit.github.io#178