For ages now, we've wanted to offer spell checking in text fields. This

has been one of our most-requested features, but we were limited due to

the capabilities and limitations of CodeMirror and the lack of browser

APIs for integrating with the spell checking dictionary. This has

remained despite my own tries to get PMs from both Chrome and Firefox

interested in opening up their vendored APIs.
Last year, we solved this integration and implemented it in our NPM

CodeMirror Speak-and-Spell library at

https://www.npmjs.com/package/@beanbag/codemirror-speak-and-spell.
This not only provides spell checking, but also enables support for the

browser's dictation and AI rewriting capabilities, amongst others, if

the browser supports them.
This change adds support for this within Review Board. There's an opt-in

feature in My Account -> Settings for enabling this, and once enabled,

text fields will support spell checking and the other listed features

in all text fields.
Spell checking applies to all text, including any code blocks. This

does not differentiate between any kinds of content within the text

field.
The feature is currently opt-in due to behavioral quirks in Chrome and

Safari. While Firefox will check spelling upon display of the text

field, Chrome and Safari will check only while typing or when clicking

on a word. This isn't specific to our implementation, but rather it can

be seen with any standard text field. That may change in time, at which

point we'd enable this by default.

Enabled and tested on Firefox, Chrome, and Safari. Worked in all three

browsers, with the quirks noted.
Tested AI rewriting and speech-to-text in iOS Safari.
Tested that behavior was normal with the setting off.