feature request: find/replace, ideally with regexp support

(Ideally it would be great to have a bidirectional API that would make it possible to use an arbitrary text editor to work on Observable notebooks and save them back to the site, but in the absence of that …)

I find the browser’s built-in facilities for searching text boxes to be barely usable, and doing search/replace in notebooks is one of the highest-friction and least pleasant tasks I routinely perform while editing notebooks (I do search/replace much more often when working on other code projects, because my text editor makes it fast and easy). It would be awesome to have an Observable-provided find/replace feature supporting replacements on either one cell at a time or the whole notebook. Especially useful would be an implementation supporting regular expressions.