webkitgtk-3.0: add metadata file
webkitgtk-3.0: add metadata file

frida/vala,rvu95/vala,rvu95/vala,rvu95/vala,GNOME/vala,flobrosch/vala-fixes,flobrosch/vala-fixes,frida/vala,GNOME/vala,spidermonkdust/vala,spidermonkdust/vala,GNOME/vala,GNOME/vala,frida/vala,frida/vala,flobrosch/vala-fixes,spidermonkdust/vala,frida/vala