bpo-33649: Add high-level APIs cheat-sheet (GH-9319)

diff --git a/Doc/library/asyncio.rst b/Doc/library/asyncio.rst
index c1b0408..25daeb6 100644
--- a/Doc/library/asyncio.rst
+++ b/Doc/library/asyncio.rst
@@ -42,8 +42,8 @@
   with async/await syntax.
 
 
-Contents
---------
+Reference
+---------
 
 .. rubric:: High-level APIs
 
@@ -73,6 +73,7 @@
 .. toctree::
    :maxdepth: 1
 
+   asyncio-api-index.rst
    asyncio-dev.rst