Use regexp2

[DRSchlaubi]

I was trying to use regex inside my config, and noticed that go doesn't support some features like (?=)

The easiest way to fix that would probably be to use this package https://pkg.go.dev/github.com/dlclark/regexp2, which has a really similar API to the stdlib regex package.

I tried updating it myself, but I ran into compiler issues related to go-gtk and since I don't have a lot of expirience with Go I gave up