small doc change to avoid json parse error

README.md

@@ -90,7 +90,7 @@ You can then write this to storage.
 To open a FlutterQuill editor with an existing JSON representation that you've previously stored, you can do something like this:
 
 ```dart
-var myJSON = jsonDecode(incomingJSONText);
+var myJSON = jsonDecode(r'$incomingJSONText');
 _controller = QuillController(
           document: Document.fromJson(myJSON),
           selection: TextSelection.collapsed(offset: 0),