📝 add mkdocs

doc/mkdocs/docs/features/merge_patch.md

@@ -0,0 +1,31 @@
+# JSON Merge Patch
+
+The library supports **JSON Merge Patch** ([RFC 7386](https://tools.ietf.org/html/rfc7386)) as a patch format. Instead of using JSON Pointer (see above) to specify values to be manipulated, it describes the changes using a syntax that closely mimics the document being modified.
+
+```cpp
+// a JSON value
+json j_document = R"({
+  "a": "b",
+  "c": {
+    "d": "e",
+    "f": "g"
+  }
+})"_json;
+
+// a patch
+json j_patch = R"({
+  "a":"z",
+  "c": {
+    "f": null
+  }
+})"_json;
+
+// apply the patch
+j_document.merge_patch(j_patch);
+// {
+//  "a": "z",
+//  "c": {
+//    "d": "e"
+//  }
+// }
+```