Add addon changes to 15.6.0 changelog (#9958)

* Add addon changes to 15.6.0 changelog

* Oops

* Add to blogpost

_posts/2017-06-13-react-v15.6.0.md

@@ -84,3 +84,12 @@ We've also published version `15.6.0` of `react` and `react-dom` on npm, and the
 * Fix issues with `onChange` not firing properly for some inputs. ([@jquense](https://github.com/jquense) in [#8575](https://github.com/facebook/react/pull/8575))
 * Fix bug where controlled number input mistakenly allowed period. ([@nhunzaker](https://github.com/nhunzaker) in [#9584](https://github.com/facebook/react/pull/9584))
 * Fix bug where performance entries were being cleared. ([@chrisui](https://github.com/chrisui) in [#9451](https://github.com/facebook/react/pull/9451))
+
+### React Addons
+
+* Fix AMD support for addons depending on `react`. ([@flarnie](https://github.com/flarnie) in [#9919](https://github.com/facebook/react/issues/9919))
+* Fix `isMounted()` to return `true` in `componentWillUnmount`. ([@mridgway](https://github.com/mridgway) in [#9638](https://github.com/facebook/react/issues/9638))
+* Fix `react-addons-update` to not depend on native `Object.assign`. ([@gaearon](https://github.com/gaearon) in [#9937](https://github.com/facebook/react/pull/9937))
+* Remove broken Google Closure Compiler annotation from `create-react-class`. ([@gaearon](https://github.com/gaearon) in [#9933](https://github.com/facebook/react/pull/9933))
+* Remove unnecessary dependency from `react-linked-input`. ([@gaearon](https://github.com/gaearon) in [#9766](https://github.com/facebook/react/pull/9766))
+* Point `react-addons-(css-)transition-group` to the new package. ([@gaearon](https://github.com/gaearon) in [#9937](https://github.com/facebook/react/pull/9937))