epd,wm: schedule a redraw on mouse clicks

but not movement.

(maybe in the future we make updates more frequent
than 2hz when mouse is moving, but not 5m after.

say, change framerate to 10 hz when mouse is moving.)

wm/seat.c

@@ -121,6 +121,12 @@ press_cursor_button(
     if (view && !view_is_transient_for(current, view)) {
       seat_set_focus(seat, view);
     }
+
+    /* Schedule a redraw in 5 ms */
+    struct cg_output *output = server->output;
+    struct epd_output *epd_output =
+      epd_output_from_output(output->wlr_output);
+    wl_event_source_timer_update(epd_output->frame_timer, 5);
   }
 }