Add support for `$urltransform` modifier

[AdamWr]

Currently it's marked as invalid:

! Error: "Unknown modifier: urltransform=/^https:\/\/af\.gog\.com\/game\//https:\/\/www.gog\.com\/game\//" in the rule: "||af.gog.com/game/$urltransform=/^https:\/\/af\.gog\.com\/game\//https:\/\/www.gog\.com\/game\//"
||af.gog.com/game/$urltransform=/^https:\/\/af\.gog\.com\/game\//https:\/\/www.gog\.com\/game\//

https://github.com/AdguardTeam/FiltersRegistry/blob/d38bb44709bbe4317272a2772c9f80ce2182b3bf/filters/filter_2_Base/diff.txt#L57-L58