Added link to 16.7 docs

Author: Brian Vaughn

content/versions.yml

@@ -1,7 +1,9 @@
 - title: '16.8'
   changelog: https://github.com/facebook/react/blob/master/CHANGELOG.md#1680-february-6-2019
 - title: '16.7'
+  path: /version/16.7
   changelog: https://github.com/facebook/react/blob/master/CHANGELOG.md#1670-december-19-2018
+  url: https://5c54aa429e16c80007af3cd2--reactjs.netlify.com/
 - title: '16.6'
   path: /version/16.6
   changelog: https://github.com/facebook/react/blob/master/CHANGELOG.md#1660-october-23-2018