add missing externs to repo

externs/webextension_polyfill/storage/Static.hx

@@ -0,0 +1,11 @@
+package webextension_polyfill.storage;
+
+typedef Static = {
+	/**
+		Fired when one or more items change.
+	**/
+	var onChanged : webextension_polyfill.events.Event<(changes:haxe.DynamicAccess<StorageChange>, areaName:String) -> Void>;
+	var sync : SyncStorageAreaSync;
+	var local : LocalStorageArea;
+	var managed : ManagedStorageArea;
+};