Add support to configure the extension the Nix way

[StellarSt0rm]

It would be amazing to have support to configure the extension from Nix config, example on how it's implemented on other extensions would be uBlock Origin.
If implemented it can easily be configured using: programs.firefox.policies."3rdparty".Extensions."{21f1ba12-47e1-4a9b-ad4e-3a0260bbeb26}" = { }

("{21f1ba12-47e1-4a9b-ad4e-3a0260bbeb26}" is the ID of the extension at the moment. it can be aquired in "about:debugging#/runtime/this-firefox")
This would be very helpful for people using NixOS, Thanks.

(If a way is already implemented please tell me!)