This splits webkit2gtk into 3 packages:
+ webkit2gtk: GTK+3 and libsoup2
+ libwebkit2gtk41: GTK+3 and libsoup3
+ libwebkit2gtk50: GTK4 and libsoup3
This is necessary since libsoup2 and libsoup3 cannot be
used at the same time.
Ideally the other packages would eventually be no longer necessary.