Add unions doc to index

Frankie Robertson · Frankie Robertson · commit a1bc7377bdb2 · 2017-10-05T11:50:09.000+03:00
diff --git a/docs/types/index.rst b/docs/types/index.rst
@@ -10,6 +10,7 @@ Types Reference
    list-and-nonnull
    interfaces
    abstracttypes
+   unions
    objecttypes
    schema
    mutations
