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

src/ol/source/Tile.js

@@ -36,6 +36,8 @@ import {scale as scaleSize, toSize} from '../size.js';
  * Abstract base class; normally only used for creating subclasses and not
  * instantiated in apps.
  * Base class for sources providing images divided into a tile grid.
+ * @template {string} EventTypes
+ * @extends Source<EventTypes>
  * @abstract
  * @api
  */