Init commit.

@types/jsdom/index.d.ts

@@ -0,0 +1,18 @@
+/// <reference path="base.d.ts"/>
+
+// eslint-disable-next-line @definitelytyped/no-declare-current-package
+declare module "jsdom" {
+    interface DOMWindow {
+        FinalizationRegistry: FinalizationRegistryConstructor;
+        WeakRef: WeakRefConstructor;
+        InputEvent: typeof InputEvent;
+        External: typeof External;
+    }
+}
+
+// Necessary to avoid breaking dependents because of the dependency
+// on the `ESNext.WeakRef` lib:
+// eslint-disable-next-line @typescript-eslint/no-empty-interface
+interface FinalizationRegistryConstructor {}
+// eslint-disable-next-line @typescript-eslint/no-empty-interface
+interface WeakRefConstructor {}