bpo-29679: Implement @contextlib.asynccontextmanager (#360)


diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst
index 4b49bfd..25afc35 100644
--- a/Doc/reference/datamodel.rst
+++ b/Doc/reference/datamodel.rst
@@ -2575,6 +2575,8 @@
       result in a :exc:`RuntimeError`.
 
 
+.. _async-context-managers:
+
 Asynchronous Context Managers
 -----------------------------