Reorganize directories (#3462)

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

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

@@ -0,0 +1,41 @@
+# <small>nlohmann::json_pointer::</small>json_pointer
+
+```cpp
+explicit json_pointer(const string_t& s = "");
+```
+
+Create a JSON pointer according to the syntax described in
+[Section 3 of RFC6901](https://tools.ietf.org/html/rfc6901#section-3).
+
+## Parameters
+
+`s` (in)
+:    string representing the JSON pointer; if omitted, the empty string is assumed which references the whole JSON value
+
+## Exceptions
+
+- Throws [parse_error.107](../../home/exceptions.md#jsonexceptionparse_error107) if the given JSON pointer `s` is 
+  nonempty and does not begin with a slash (`/`); see example below.
+- Throws [parse_error.108](../../home/exceptions.md#jsonexceptionparse_error108) if a tilde (`~`) in the given JSON
+  pointer `s` is not followed by `0` (representing `~`) or `1` (representing `/`); see example below.
+
+## Examples
+
+??? example
+
+    The example shows the construction several valid JSON pointers as well as the exceptional behavior.
+     
+    ```cpp
+    --8<-- "examples/json_pointer.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/json_pointer.output"
+    ```
+
+## Version history
+
+- Added in version 2.0.0.
+- Changed type of `s` to `string_t` in version 3.11.0.