Add card-wide action support for timeline.

src/action-handler-directive.ts

@@ -153,6 +153,7 @@ class ActionHandler extends HTMLElement implements ActionHandler {
     element.addEventListener('touchcancel', end);
 
     element.addEventListener('mousedown', start, { passive: true });
+    element.addEventListener('pointerdown', start, { passive: true });
     element.addEventListener('click', end);
 
     element.addEventListener('keyup', handleEnter);