Gello: Add DuckDuckGo search engine to ES locale

Change-Id: I26184da8ca9374417e74c26341d5515aea9918b2
diff --git a/res/values-es-rES/donottranslate-search_engines.xml b/res/values-es-rES/donottranslate-search_engines.xml
index 053d786..848fb7e 100644
--- a/res/values-es-rES/donottranslate-search_engines.xml
+++ b/res/values-es-rES/donottranslate-search_engines.xml
@@ -28,5 +28,6 @@
     <item>yahoo_es</item>
     <item>terra_es</item>
     <item>hispavista</item>
+    <item>duckduckgo</item>
   </string-array>
 </resources>