Add __all__ for modules beginning with 'u', 'x', 'w' and 'z' (#7374)

stdlib/zipimport.pyi

@@ -7,6 +7,9 @@ from typing import Any
 if sys.version_info >= (3, 7):
     from importlib.abc import ResourceReader
 
+if sys.version_info >= (3, 8):
+    __all__ = ["ZipImportError", "zipimporter"]
+
 class ZipImportError(ImportError): ...
 
 class zipimporter: