non blocking functions added (#62)

examples/LoRaSenderNonBlocking/LoRaSenderNonBlocking.ino

@@ -0,0 +1,35 @@
+#include <SPI.h>
+#include <LoRa.h>
+
+int counter = 0;
+
+void setup() {
+  Serial.begin(9600);
+  while (!Serial);
+
+  Serial.println("LoRa Sender non-blocking");
+
+  if (!LoRa.begin(915E6)) {
+    Serial.println("Starting LoRa failed!");
+    while (1);
+  }
+}
+
+void loop() {
+  // wait until the radio is ready to send a packet
+  while (LoRa.beginPacket() == 0) {
+    Serial.print("waiting for radio ... ");
+    delay(100);
+  }
+
+  Serial.print("Sending packet non-blocking: ");
+  Serial.println(counter);
+
+  // send in async / non-blocking mode
+  LoRa.beginPacket();
+  LoRa.print("hello ");
+  LoRa.print(counter);
+  LoRa.endPacket(true); // true = async / non-blocking mode
+
+  counter++;
+}