transparent: add transparency

[MAFiA303]

i found this repo it can add transparency to firefox.
thought you can ingest it into ffgx

[Godiesc]

Hi, AFAIK, transparency support on Windows OS ended a few versions ago, when Win7 support ended, I read that the ESR version of Firefox still has that feature; on MacOS I saw that it can still work with transparency, and on Linux I don't know.