Add __all__ to modules beginning with 'j', 'k' and 'l' (#7328)

stdlib/keyword.pyi

@@ -1,6 +1,11 @@
 import sys
 from typing import Sequence
 
+if sys.version_info >= (3, 9):
+    __all__ = ["iskeyword", "issoftkeyword", "kwlist", "softkwlist"]
+else:
+    __all__ = ["iskeyword", "kwlist"]
+
 def iskeyword(s: str) -> bool: ...
 
 kwlist: Sequence[str]