update API documentation to the language parameter to search

views/documentation/documentation.haml

@@ -151,6 +151,7 @@
               %li include={prefLabel, synonym, definition, notation, cui, semanticType} // default = (see Common Parameters section)
               %li page={integer representing the page number} // default = 1
               %li pagesize={integer representing the size of the returned page} // default = 50
+              %li language={an ISO 639-1 language value, e.g 'fr' or 'en'} // by default search in all languages
 
         %h4#nav_search_subtree Subtree Search