editor: Add keyboard_focus handler to schedule repaint
editor: Add keyboard_focus handler to schedule repaint

This let the editor client repaint the frame to indicate it's active
when it receives keyboard focus.

udoprog/weston,giucam/weston,Tarnyko/weston-xdg_surface_present,Tarnyko/weston-xdg_surface_present,mchalupa/weston,Fantu/compositor-spice,kwm81/weston,sir-murray/weston,krezovic/weston,jonnylamb/weston,xorgy/weston,udoprog/weston,krezovic/weston,kwm81/weston,sir-murray/weston,Gnurou/weston,Fantu/compositor-spice,Gnurou/weston,Fantu/compositor-spice,mchalupa/weston,giucam/weston,eyolfson/weston,eyolfson/weston,xorgy/weston,jonnylamb/weston