Add links to reference implementation and demo

Author: cdce8p

peps/pep-0824.rst

@@ -315,8 +315,8 @@ Reference Implementation
 ========================
 
 A reference implementation is available at
-https://github.com/cdce8p/cpython/tree/pep-XXX. A online demo can be
-tested at https://pepXXX-demo.pages.dev/.
+https://github.com/cdce8p/cpython/tree/pep824-none-coalescing-operators.
+A online demo can be tested at https://pep823-and-pep824-demo.pages.dev/.
 
 
 Deferred Ideas