Add 2.1.2 release notes

docs/releases/index.rst

@@ -25,6 +25,7 @@ Supported Versions:
 .. toctree::
     :maxdepth: 1
 
+    v2.1.2
     v2.1.1
     v2.1.0
     v2.0.0

docs/releases/v2.1.2.rst

@@ -0,0 +1,8 @@
+v2.1.2 release notes
+====================
+
+Bug fixes:
+
+* Instead of throwing a server error, return None if "Latest Pages" block has invalid (i.e. deleted) classifier term.
+
+* Fix display issue with classifier terms in Wagtail Admin when editing a page.