Alerts do not work on wikis

[skullbunnygalaxy]

Previously when I researched this, I encountered many comments stating this is a known issue, which implies it should work but currently doesn't. However, I found that there was no open issue for this at what appears to be the relevant repo. I opened an issue for it there: github/markup#1727

This issue here is just for tracking purposes since the feature working is reliant on Github.