Sandbox all the WebKit!

Hi,

Please help GNOME sandbox all its uses of WebKit! We're about halfway 
done:

https://gitlab.gnome.org/GNOME/Initiatives/-/issues/19

If you maintain an application using WebKit that hasn't yet enabled the 
sandbox, it usually only requires one or two lines of code. 
Applications that use a web process extension may be more complicated, 
but we don't have many of those.

Michael