Update README.md

Author: alexhunsley

README.md

@@ -10,7 +10,11 @@ Example:
     // This step doesn't do the actual patching!
 
     let patchedJSONContent: PatchedJSON = Content(fileURL: someJSONFileURL) {
+
         Add(address: "/users/-", jsonContent: "alex")
+        Add(address: "/users/-", jsonContent: [1, "hi", 5.0])
+        // note: please use `null` and never `nil` to mean JSON's `null`
+        Add(address: "/users/-", jsonContent: null)
 
         Remove(address: "/temp/log")