ws: Add minimal Python WebKit2 browser as preferred alternative
ws: Add minimal Python WebKit2 browser as preferred alternative

If Python3, GI, GTK3, and WebKit2 are installed, use these to show an
embedded web view, instead of Firefox or Chromium. This provides a much
nicer impression of a "desktop web app".

Closes #10770

mvollmer/cockpit,garrett/cockpit,deryni/cockpit,garrett/cockpit,garrett/cockpit,garrett/cockpit,deryni/cockpit,mvollmer/cockpit,deryni/cockpit,deryni/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,andreasn/cockpit,cockpit-project/cockpit,mvollmer/cockpit,martinpitt/cockpit,martinpitt/cockpit,deryni/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,andreasn/cockpit,deryni/cockpit,andreasn/cockpit,mvollmer/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,andreasn/cockpit,cockpituous/cockpit,cockpituous/cockpit,deryni/cockpit,andreasn/cockpit,cockpituous/cockpit,garrett/cockpit,andreasn/cockpit,cockpit-project/cockpit,martinpitt/cockpit,mvollmer/cockpit,cockpituous/cockpit,moraleslazaro/cockpit,cockpituous/cockpit,martinpitt/cockpit,cockpituous/cockpit,andreasn/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit