Updated nlohmann::basicjson (markdown)

nlohmann::basicjson.md

@@ -94,6 +94,10 @@ Note the type `json` is a typedef for the class `basic_json` with its default ty
 
 - `at`
 - `operator[]`
+- [**front**](https://github.com/nlohmann/json/wiki/nlohmann::basicjson::front)<br>
+  access the first element
+- [**back**](https://github.com/nlohmann/json/wiki/nlohmann::basicjson::back)<br>
+  access the last element
 
 ### Iterators