Added subscribe functionality

examples/AntaresMQTTSubscribe/AntaresMQTTSubscribe.ino

@@ -0,0 +1,30 @@
+#include <AntaresESP8266MQTT.h>
+
+#define ACCESSKEY "your-access-key"
+#define WIFISSID "your-wifi-ssid"
+#define PASSWORD "your-wifi-password"
+
+#define projectName = "your-project-name";
+#define deviceName = "your-device-name";
+
+AntaresESP8266MQTT antares(ACCESSKEY);
+
+void callback(char topic[], byte payload[], unsigned int length) {
+  String topicString = String(topic);
+  String payloadString = antares.byteToString(payload, length);
+  
+  Serial.println("[ANTARES] New Mesage: ");
+  Serial.println(topicString);
+  Serial.println(payloadString);
+}
+
+void setup() {
+  Serial.begin(115200);
+  antares.setDebug(true);
+  antares.wifiConnection(WIFISSID, PASSWORD);
+  antares.setMqttServer();
+  antares.setCallback(callback);
+}
+void loop() {
+  antares.checkMqttConnection();
+}