[Feature] Upgrade useragent spoofing

[Albirew]

Instead of default custom, and 4 chrome lines (total 6 lines), i believe it would be nicer to make only 3 lines like this:
⭕ Default
⭕ Spoof [browser list dropdown] on [OS list dropdown]
⭕ Custom

what do you think?
This would allow users to spoof firefox on windows or linux for example (i'll NEVER spoof chrome useragent since it can give it more stats, hence more popularity)