Make changes to check for broken links

[vincerubinetti]

@jmcmurry

Closes #3

Note that there is a bit limitation to this, in that it only goes to the URL and checks the status code. If you go to a broken Zoom link, for example, this won't catch it because Zoom doesn't return the appropriate status code (it returns 200 as if everything is OK). For the specific case of Zoom, I could check the HTML on the page for the presence "Invalid meeting ID", but that is a brittle solution. They may change that warning text at some point, or even theoretically include the word "invalid" somewhere on a valid meeting page for some reason.

However, I ran this locally on the large Bridge2AI redirects, and it did seem to catch two non-existing Google docs. Just keep in mind that this is a rough check. There may be false positives/negatives. As such, I split it up as a separate workflow check, so if you see the "encode" workflow fail, that is a critical error you definitely need to fix, but if you see the "check" workflow fail, you may be able to ignore that.

[vincerubinetti]

@falquaddoomi Poke for review. Not urgent at all, but I'd like to close the loop if you have time.

[falquaddoomi]

I didn't see anything that would block approval, but I left a comment about core.js.