Update comments in examples (#457)

It's seems not that important, but this helps the new user understand the code.

examples/Ntag216_AUTH/Ntag216_AUTH.ino

@@ -26,7 +26,7 @@ void setup() {
 }
 
 void loop() {
-  // Look for new cards
+  // Reset the loop if no new card present on the sensor/reader. This saves the entire process when idle.
   if ( ! mfrc522.PICC_IsNewCardPresent()) {
     return;
   }
@@ -55,4 +55,4 @@ void loop() {
   mfrc522.PICC_DumpMifareUltralightToSerial(); //This is a modifier dunp just cghange the for cicle to < 232 instead of < 16 in order to see all the pages on NTAG216
 
   delay(3000);
-}
+}