Add empty stubs for xml.dom.* modules. (#3856)

stdlib/2and3/xml/dom/minidom.pyi

@@ -0,0 +1,3 @@
+from typing import Any
+
+def __getattr__(name: str) -> Any: ...  # incomplete

stdlib/2and3/xml/dom/pulldom.pyi

@@ -0,0 +1,3 @@
+from typing import Any
+
+def __getattr__(name: str) -> Any: ...  # incomplete