io/router,widget: give every key.InputOp a chance to process events

If the currently focused handler don't want the key event, try every
other handler, from top to bottom. This change requires widgets to
only react when focused.

Fixes: https://todo.sr.ht/~eliasnaur/gio/406
Signed-off-by: Elias Naur <mail@eliasnaur.com>

widget/enum.go

@@ -98,7 +98,7 @@ func (e *Enum) Layout(gtx layout.Context, k string, content layout.Widget) layou
 				e.focused = false
 			}
 		case key.Event:
-			if ev.State != key.Release {
+			if !e.focused || ev.State != key.Release {
 				break
 			}
 			if ev.Name != key.NameEnter && ev.Name != key.NameSpace {