Add 16.6 to versions (#1287)

Author: gaearon

content/versions.yml

@@ -1,5 +1,9 @@
+- title: '16.6'
+  changelog: https://github.com/facebook/react/blob/master/CHANGELOG.md#1660-october-23-2018
 - title: '16.5'
+  path: /version/16.5
   changelog: https://github.com/facebook/react/blob/master/CHANGELOG.md#1650-september-5-2018
+  url: https://5bcf5863c6aed64970d6de5b--reactjs.netlify.com/
 - title: '16.4'
   path: /version/16.4
   changelog: https://github.com/facebook/react/blob/master/CHANGELOG.md#1640-may-23-2018
@@ -19,4 +23,4 @@
 - title: '16.0'
   path: /version/16.0
   url: https://5a046bf5a6188f4b8fa4938a--reactjs.netlify.com
-  changelog: https://github.com/facebook/react/blob/master/CHANGELOG.md#1600-september-26-2017
+  changelog: https://github.com/facebook/react/blob/master/CHANGELOG.md#1600-september-26-2017