Now that #91724 is merged, it would be nice to have a set of Firefox extensions, that one could easily pick from.

Some aspects have been discussed in the PR already, but making a separate issue seems better.
The main reason for packaging is (#91724 (comment))

They're some of the most security critical and most used programs, I think packaging them would be a good idea.

We could make it a part of nixpkgs, e.g. nixpkgs.firefoxExtensions...., but there some things to keep in mind.

1. Automatically updating them some way ( e.g. like rycee does here https://gitlab.com/rycee/nur-expressions/-/tree/master/pkgs/firefox-addons )
2. Backporting to stable
3. Channels that hang (mostly unstable - security risk, but this is a general thing...)
4. Will create a lot of PRs? One each day or something maybe.

A solution could be, to have it as a separate repository.