Yes, we will land on Firefox very soon, hopefully next month.
Copilot's been very useful. The extension is built on TS and lots of custom CSS. Codex is knowledgeable with browser extension APIs and it's helped me to write most CSS utility classes that change sizes, margins and paddings, so that I don't have to bundle the extension with another third-party library.
I've written extensions before and Firefox has a very good polyfill [0] that makes it quite easy to write extensions for all browsers. It does get a bit trickier if you also want to incorporate TypeScript [1] or React however.
Copilot's been very useful. The extension is built on TS and lots of custom CSS. Codex is knowledgeable with browser extension APIs and it's helped me to write most CSS utility classes that change sizes, margins and paddings, so that I don't have to bundle the extension with another third-party library.