Updated nlohmann::basicjson::size (markdown)

nlohmann::basicjson::size.md

@@ -55,4 +55,6 @@ values contains 4 elements.
 
 ## See also
 
-- [size](nlohmann::basicjson::size)
+- [empty](https://github.com/nlohmann/json/wiki/nlohmann::basicjson::empty)<br>
+checks whether the container is empty<br>
+public member function