Add updated changelog to readme.txt

Author: sheabunge

readme.txt

@@ -119,6 +119,12 @@ That's fantastic! Fork the [repository on GitHub](http://github.com/sheabunge/co
 
 == Changelog ==
 
+= 2.7.1 =
+* Added Dutch translation by Sander Spies
+* Ensured that the editor theme setting is properly validated. Thanks to [Netsparker](https://www.netsparker.com) for reporting.
+* Ensured that snippet tags are properly escaped. Thanks to [Netsparker](https://www.netsparker.com) for reporting.
+* Updated CodeMirror to version 5.19.0
+
 = 2.7.0 =
 * Fixed plugin translations being loaded
 * Increase default snippets per page so that all are usually shown