Add __all__ for modules beginning with 'h' and 'i' (#7327)

stdlib/html/parser.pyi

@@ -1,6 +1,8 @@
 from _markupbase import ParserBase
 from typing import Pattern
 
+__all__ = ["HTMLParser"]
+
 class HTMLParser(ParserBase):
     def __init__(self, *, convert_charrefs: bool = ...) -> None: ...
     def feed(self, data: str) -> None: ...