package as a firefox extension

[nickolasclarke]

I'd love to use this is on FF as well. I've never ported a chrome extension, but I suspect for this simple of a codebase it may not be too bad. If I find the time to attempt it, I'll also open a PR. If someone else knows how to do this quickly, dont hold your breath for me.

[PabloRomanH]

Please do open the PR if you have the time!