Update comments in examples (#457)

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

examples/ChangeUID/ChangeUID.ino

@@ -61,7 +61,7 @@ void setup() {
 // But of course this is a more proper approach
 void loop() {
   
-  // Look for new cards, and select one if present
+  // Reset the loop if no new card present on the sensor/reader. This saves the entire process when idle. And if present, select one.
   if ( ! mfrc522.PICC_IsNewCardPresent() || ! mfrc522.PICC_ReadCardSerial() ) {
     delay(50);
     return;

examples/DumpInfo/DumpInfo.ino

@@ -51,7 +51,7 @@ 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;
 	}

examples/MifareClassicValueBlock/MifareClassicValueBlock.ino

@@ -65,7 +65,7 @@ void setup() {
  * Main loop.
  */
 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;
 

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;
   }

examples/ReadAndWrite/ReadAndWrite.ino

@@ -64,7 +64,7 @@ void setup() {
  * Main loop.
  */
 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;
 

examples/ReadNUID/ReadNUID.ino

@@ -57,7 +57,7 @@ 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 ( ! rfid.PICC_IsNewCardPresent())
     return;
 

examples/rfid_default_keys/rfid_default_keys.ino

@@ -119,7 +119,7 @@ bool try_key(MFRC522::MIFARE_Key *key)
  * Main loop.
  */
 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;
 

examples/rfid_read_personal_data/rfid_read_personal_data.ino

@@ -49,7 +49,7 @@ 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;
   }

examples/rfid_write_personal_data/rfid_write_personal_data.ino

@@ -40,7 +40,7 @@ void loop() {
   MFRC522::MIFARE_Key key;
   for (byte i = 0; i < 6; i++) key.keyByte[i] = 0xFF;
 
-  // 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;
   }