add arduino json lib

#182

lib/ArduinoJson/examples/JsonGeneratorExample/JsonGeneratorExample.ino

@@ -0,0 +1,81 @@
+// ArduinoJson - arduinojson.org
+// Copyright Benoit Blanchon 2014-2018
+// MIT License
+//
+// This example shows how to generate a JSON document with ArduinoJson.
+
+#include <ArduinoJson.h>
+
+void setup() {
+  // Initialize Serial port
+  Serial.begin(9600);
+  while (!Serial) continue;
+
+  // Memory pool for JSON object tree.
+  //
+  // Inside the brackets, 200 is the size of the pool in bytes.
+  // Don't forget to change this value to match your JSON document.
+  // Use arduinojson.org/assistant to compute the capacity.
+  StaticJsonBuffer<200> jsonBuffer;
+
+  // StaticJsonBuffer allocates memory on the stack, it can be
+  // replaced by DynamicJsonBuffer which allocates in the heap.
+  //
+  // DynamicJsonBuffer  jsonBuffer(200);
+
+  // Create the root of the object tree.
+  //
+  // It's a reference to the JsonObject, the actual bytes are inside the
+  // JsonBuffer with all the other nodes of the object tree.
+  // Memory is freed when jsonBuffer goes out of scope.
+  JsonObject& root = jsonBuffer.createObject();
+
+  // Add values in the object
+  //
+  // Most of the time, you can rely on the implicit casts.
+  // In other case, you can do root.set<long>("time", 1351824120);
+  root["sensor"] = "gps";
+  root["time"] = 1351824120;
+
+  // Add a nested array.
+  //
+  // It's also possible to create the array separately and add it to the
+  // JsonObject but it's less efficient.
+  JsonArray& data = root.createNestedArray("data");
+  data.add(48.756080);
+  data.add(2.302038);
+
+  root.printTo(Serial);
+  // This prints:
+  // {"sensor":"gps","time":1351824120,"data":[48.756080,2.302038]}
+
+  Serial.println();
+
+  root.prettyPrintTo(Serial);
+  // This prints:
+  // {
+  //   "sensor": "gps",
+  //   "time": 1351824120,
+  //   "data": [
+  //     48.756080,
+  //     2.302038
+  //   ]
+  // }
+}
+
+void loop() {
+  // not used in this example
+}
+
+// See also
+// --------
+//
+// The website arduinojson.org contains the documentation for all the functions
+// used above. It also includes an FAQ that will help you solve any
+// serialization problem.
+// Please check it out at: https://arduinojson.org/
+//
+// The book "Mastering ArduinoJson" contains a tutorial on serialization.
+// It begins with a simple example, like the one above, and then adds more
+// features like serializing directly to a file or an HTTP request.
+// Please check it out at: https://arduinojson.org/book/