Fix type and documentation of style function

src/ol/style/Style.js

@@ -13,9 +13,10 @@ import Stroke from './Stroke.js';
  * A function that takes an {@link module:ol/Feature} and a `{number}`
  * representing the view's resolution. The function should return a
  * {@link module:ol/style/Style} or an array of them. This way e.g. a
- * vector layer can be styled.
+ * vector layer can be styled. If the function returns `undefined`, the
+ * feature will not be rendered.
  *
- * @typedef {function(import("../Feature.js").FeatureLike, number):(Style|Array<Style>)} StyleFunction
+ * @typedef {function(import("../Feature.js").FeatureLike, number):(Style|Array<Style>)|undefined} StyleFunction
  */
 
 /**