README: Add link to LICENSE (GH-21565)

Thanks @wbnns for your contribution.

Author: wbnns

README.rst

@@ -259,8 +259,9 @@ rights reserved.
 
 Copyright (c) 1991-1995 Stichting Mathematisch Centrum.  All rights reserved.
 
-See the file "LICENSE" for information on the history of this software, terms &
-conditions for usage, and a DISCLAIMER OF ALL WARRANTIES.
+See the `LICENSE <https://github.com/python/cpython/blob/master/LICENSE>`_ for
+information on the history of this software, terms & conditions for usage, and a
+DISCLAIMER OF ALL WARRANTIES.
 
 This Python distribution contains *no* GNU General Public License (GPL) code,
 so it may be used in proprietary projects.  There are interfaces to some GNU