issue 20091 - index entry for __main__ in runpy docs.

Doc/library/runpy.rst

@@ -28,6 +28,9 @@ The :mod:`runpy` module provides two functions:
 
 .. function:: run_module(mod_name, init_globals=None, run_name=None, alter_sys=False)
 
+   .. index::
+      module: __main__
+
    Execute the code of the specified module and return the resulting module
    globals dictionary. The module's code is first located using the standard
    import mechanism (refer to :pep:`302` for details) and then executed in a
@@ -87,6 +90,9 @@ The :mod:`runpy` module provides two functions:
 
 .. function:: run_path(file_path, init_globals=None, run_name=None)
 
+   .. index::
+      module: __main__
+
    Execute the code at the named filesystem location and return the resulting
    module globals dictionary. As with a script name supplied to the CPython
    command line, the supplied path may refer to a Python source file, a