Describe config file validation in release notes

doc/releasenotes.rst

@@ -6,3 +6,5 @@ Version 0.2
 
 * Python 2 support, thanks to `Johannes Baiter <https://github.com/jbaiter>`_
 * Ability to define multiple shortcuts for one application.
+* Validate config files to produce more helpful errors, thanks to
+  `Tom Wallroth <https://github.com/devsnd>`_.