This is not for real, just a test page!
And (gasp!) it's been edited! (again!)
<p>Ok, so how does this handle <a href="https://html.spec.whatwg.org/multipage/">HTML</a> tags in the main page? Does it (as I'd want) properly entity-encode the tags so it's always treated as content, or pass it through as-is such that on the next edit it gets interpreted as part of the page markup? We shall see!</p>
Ok, that much is fixed now. How about some JS code samples too?
var foo = 'cows and magic stuff!';
var bar = 'and don't forget Bob\'s Burgers...';
window.alert(foo + bar);