Add docs for 2.1.1

docs/releases/index.rst

@@ -25,6 +25,7 @@ Supported Versions:
 .. toctree::
     :maxdepth: 1
 
+    v2.1.1
     v2.1.0
     v2.0.0
     v1.0.3

docs/releases/v2.1.1.rst

@@ -0,0 +1,4 @@
+v2.1.1 release notes
+====================
+
+This release fixes a packaging issue that was published to PyPI with 2.1.0. All installations of 2.1.0 should use 2.1.1 instead.