Merge pull request #12416 from ahocevar/eventtype-generics

Use generics to limit event types in on(), once() and un()

src/ol/Overlay.js

@@ -101,6 +101,7 @@ const Property = {
  *     popup.setPosition(coordinate);
  *     map.addOverlay(popup);
  *
+ * @extends BaseObject<'change:element'|'change:map'|'change:offset'|'change:position'|'change:positioning'>
  * @api
  */
 class Overlay extends BaseObject {