Updated nlohmann::basicjson::end (markdown)

nlohmann::basicjson::end.md

@@ -8,6 +8,8 @@ const_iterator cend() const;
 
 Returns an iterator to the element following the last element of the container. This element acts as a placeholder; attempting to access it results in undefined behavior.
 
+![illustration of iterators](http://upload.cppreference.com/mwiki/images/1/1b/range-begin-end.svg)
+
 ## Parameters
 
 None.