Add `repository` and `license` in `library.properties` (closes #662)

library.properties

@@ -7,3 +7,5 @@ paragraph=ArduinoJson supports ✔ serialization, ✔ deserialization, ✔ fixed
 category=Data Processing
 url=https://arduinojson.org/?utm_source=meta&utm_medium=library.properties
 architectures=*
+repository=https://github.com/bblanchon/ArduinoJson.git
+license=MIT