Created nlohmann::basicjson::is_string (markdown)

nlohmann::basicjson::is_string.md

@@ -0,0 +1,36 @@
+```cpp
+bool is_string() const;
+```
+
+## Description
+
+Returns whether JSON container has type string.
+
+## Parameters
+
+None.
+
+## Return value
+
+`true` of value type is string, `false` otherwise.
+
+## Complexity
+
+Constant.
+
+## Exceptions
+
+None. The function's noexcept-specification is `noexcept`.
+
+## See also
+
+- [**is_null**](https://github.com/nlohmann/json/wiki/nlohmann::basicjson::is_null)<br>
+  whether value is null
+- [**is_boolean**](https://github.com/nlohmann/json/wiki/nlohmann::basicjson::is_boolean)<br>
+  whether value is boolean
+- [**is_number**](https://github.com/nlohmann/json/wiki/nlohmann::basicjson::is_number)<br>
+  whether value is number
+- [**is_object**](https://github.com/nlohmann/json/wiki/nlohmann::basicjson::is_object)<br>
+  whether value is object
+- [**is_array**](https://github.com/nlohmann/json/wiki/nlohmann::basicjson::is_array)<br>
+  whether value is array