We've been running CodeMirror 3.20, but there's been quite a few

releases since then. These have focused on speed, bug fixes,

compatibility, and a bunch of things we honestly don't care about right

now.

Tested various Markdown formatting and list continuation.
Tested auto-growing the text field for the fields that use that,

and tested places like the comment dialog.
Note that I've left out the new minified JS for CodeMirror 4.2 from

the review request, but it's in the commit.