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

diff --git a/Doc/library/asyncio-subprocess.rst b/Doc/library/asyncio-subprocess.rst
index 92c081b..ef8a1cb 100644
--- a/Doc/library/asyncio-subprocess.rst
+++ b/Doc/library/asyncio-subprocess.rst
@@ -9,6 +9,8 @@
 This section describes high-level async/await asyncio APIs to
 create and manage subprocesses.
 
+.. _asyncio_example_subprocess_shell:
+
 Here's an example of how asyncio can run a shell command and
 communicate its result back::