Reorganize directories (#3462)

* 🚚 move files
* 🚚 rename doc folder to docs
* 🚚 rename test folder to tests

docs/mkdocs/docs/api/json_pointer/to_string.md

@@ -0,0 +1,40 @@
+# <small>nlohmann::json_pointer::</small>to_string
+
+```cpp
+string_t to_string() const;
+```
+
+Return a string representation of the JSON pointer.
+
+## Return value
+
+A string representation of the JSON pointer
+
+## Notes
+
+For each JSON pointer `ptr`, it holds:
+
+```cpp
+ptr == json_pointer(ptr.to_string());
+```
+
+## Examples
+
+??? example
+
+    The example shows the result of `to_string`.
+     
+    ```cpp
+    --8<-- "examples/json_pointer__to_string.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/json_pointer__to_string.output"
+    ```
+
+## Version history
+
+- Since version 2.0.0.
+- Changed return type to `string_t` in version 3.11.0.