Reorganize directories (#3462)

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

docs/mkdocs/docs/features/merge_patch.md

@@ -0,0 +1,20 @@
+# JSON Merge Patch
+
+The library supports JSON Merge Patch ([RFC 7386](https://tools.ietf.org/html/rfc7386)) as a patch format.
+The merge patch format is primarily intended for use with the HTTP PATCH method as a means of describing a set of modifications to a target resource's content. This function applies a merge patch to the current JSON value.
+
+Instead of using [JSON Pointer](json_pointer.md) to specify values to be manipulated, it describes the changes using a syntax that closely mimics the document being modified.
+
+??? example
+
+    The following code shows how a JSON Merge Patch is applied to a JSON document.
+
+    ```cpp
+    --8<-- "examples/merge_patch.cpp"
+    ```
+    
+    Output:
+
+    ```json
+    --8<-- "examples/merge_patch.output"
+    ```