Add release note sections for 1.12.2

CHANGELOG.txt

@@ -16,6 +16,10 @@ Changelog
  * Fix: Fixed avatar position in footer on mobile (Jack Paine)
 
 
+1.12.2 (xx.xx.xxxx) - IN DEVELOPMENT
+~~~~~~~~~~~~~~~~~~~
+
+
 1.12.1 (30.08.2017)
 ~~~~~~~~~~~~~~~~~~~
 

docs/releases/1.12.2.rst

@@ -0,0 +1,15 @@
+=============================================
+Wagtail 1.12.2 release notes - IN DEVELOPMENT
+=============================================
+
+.. contents::
+    :local:
+    :depth: 1
+
+
+What's new
+==========
+
+Bug fixes
+~~~~~~~~~
+

docs/releases/index.rst

@@ -6,6 +6,7 @@ Release notes
 
    upgrading
    1.13
+   1.12.2
    1.12.1
    1.12
    1.11.1