chore: 2.1.2 release notes

Author: fgmacedo

docs/releases/2.1.2.md

@@ -0,0 +1,14 @@
+# StateMachine 2.1.2
+
+*October  6, 2023*
+
+This release improves the setup performance of the library by a 10x factor, with a major
+refactoring on how we handle the callbacks registry and validations.
+
+See [#401](https://github.com/fgmacedo/python-statemachine/issues/401) for the technical details.
+
+
+## Bugfixes in 2.1.2
+
+- Fixes [#406](https://github.com/fgmacedo/python-statemachine/issues/406) action callback being
+  called twice when mixing decorator syntax combined with the naming convention.

docs/releases/index.md

@@ -13,8 +13,9 @@ Below are release notes through StateMachine and its patch releases.
 ###  2.0 releases
 
 ```{toctree}
-:maxdepth: 1
+:maxdepth: 2
 
+2.1.2
 2.1.1
 2.1.0
 2.0.0