Allow GTK4 builds of webkit
Currently, you only allow webkit2gtk 4.0 (soup2 gtk3) or 4.1 (soup3 gtk3). However, there is also webkitgtk 6.0, which is the GTK4 port of webkitgtk.
Currently, you only allow webkit2gtk 4.0 (soup2 gtk3) or 4.1 (soup3 gtk3). However, there is also webkitgtk 6.0, which is the GTK4 port of webkitgtk.