Add Jekyll link checking into our GitHub Actions.

[lewisgross1296]

The CNERG website has many links, so it would be worth adding a step to our GitHub Actions to test the validity and report failues.

@MicahGale provided this resource as a start. I'm not super experienced w GHA or jekyll, but maybe we could spend some time at #hacker-within discussing this addition.

I might have a chance to give it a go eventually but am little busy for a while. Open to others trying to implement this first, if they have the time. Maybe @bquan0 or @bennibbelink would be interested? (no pressure if you're busy too)

[MicahGale]

I was about to open this issue as well, since it is really a separate task as you mentioned.