feat(indev) Add crown support to pointer input device (#5057)

src/core/lv_obj_event.h

@@ -151,6 +151,13 @@ const lv_area_t * lv_event_get_old_size(lv_event_t * e);
  */
 uint32_t lv_event_get_key(lv_event_t * e);
 
+/**
+ * Get the signed rotary encoder diff. passed as parameter to an event. Can be used in `LV_EVENT_ROTARY`
+ * @param e     pointer to an event
+ * @return      the triggering key or NULL if called on an unrelated event
+ */
+int32_t lv_event_get_rotary_diff(lv_event_t * e);
+
 /**
  * Get the animation descriptor of a scrolling. Can be used in `LV_EVENT_SCROLL_BEGIN`
  * @param e     pointer to an event