Added links to the ArduinoJson assistant (issue #513)

README.md

@@ -58,6 +58,8 @@ double longitude   = root["data"][1];
 
 [See JsonParserExample.ino](examples/JsonParserExample/JsonParserExample.ino)
 
+Use [ArduinoJson Assistant](https://bblanchon.github.io/ArduinoJson/assistant/) to compute the buffer size.
+
 #### Encoding / Generating
 
 ```c++
@@ -78,6 +80,8 @@ root.printTo(Serial);
 
 [See JsonGeneratorExample.ino](examples/JsonGeneratorExample/JsonGeneratorExample.ino)
 
+Use [ArduinoJson Assistant](https://bblanchon.github.io/ArduinoJson/assistant/) to compute the buffer size.
+
 
 Documentation
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