Add generic support to Element.closest() (#697)

* Add generic support to `Element.closest()`

* Update widlprocess.ts

#696 (comment)

* Add generated files

Author: Federico Brigante

baselines/dom.generated.d.ts

@@ -5039,7 +5039,7 @@ interface Element extends Node, ParentNode, NonDocumentTypeChildNode, ChildNode,
      */
     closest<K extends keyof HTMLElementTagNameMap>(selector: K): HTMLElementTagNameMap[K] | null;
     closest<K extends keyof SVGElementTagNameMap>(selector: K): SVGElementTagNameMap[K] | null;
-    closest(selector: string): Element | null;
+    closest<E extends Element = Element>(selector: string): E | null;
     /**
      * Returns element's first attribute whose qualified name is qualifiedName, and null if there is no such attribute otherwise.
      */

inputfiles/addedTypes.json

@@ -732,7 +732,7 @@
                             "override-signatures": [
                                 "closest<K extends keyof HTMLElementTagNameMap>(selector: K): HTMLElementTagNameMap[K] | null",
                                 "closest<K extends keyof SVGElementTagNameMap>(selector: K): SVGElementTagNameMap[K] | null",
-                                "closest(selector: string): Element | null"
+                                "closest<E extends Element = Element>(selector: string): E | null"
                             ]
                         },
                         "insertAdjacentElement": {