docs/library/builtins.rst: Add module title.

jimmo · dpgeorge · commit af162257d377 · 2021-08-17T11:26:24.000+10:00
This fixes the rendering on library/index.rst.

Signed-off-by: Jim Mussared &lt;jim.mussared@gmail.com&gt;
diff --git a/docs/library/builtins.rst b/docs/library/builtins.rst
@@ -1,5 +1,5 @@
-Builtin functions and exceptions
-================================
+:mod:`builtins` -- builtin functions and exceptions
+===================================================
 
 All builtin functions and exceptions are described here. They are also
 available via ``builtins`` module.
