✨ implemented JSON Merge Patch (RFC 7396)

SQLite's json1 extension (https://www.sqlite.org/json1.html) supports JSON Merge Patch (https://tools.ietf.org/html/rfc7396). As the implementation is trivial and we already support JSON Patch, I think this could be a nice extension to the library.

doc/examples/merge_patch.output

@@ -0,0 +1,11 @@
+{
+    "author": {
+        "givenName": "John"
+    },
+    "content": "This will be unchanged",
+    "phoneNumber": "+01-123-456-7890",
+    "tags": [
+        "example"
+    ],
+    "title": "Hello!"
+}