Added a coupon code for the book

examples/JsonConfigFile/JsonConfigFile.ino

@@ -133,12 +133,12 @@ void loop() {
 // See also
 // --------
 //
-// The website arduinojson.org contains the documentation for all the functions
+// https://arduinojson.org/ contains the documentation for all the functions
 // used above. It also includes an FAQ that will help you solve any
 // serialization or deserialization problem.
-// Please check it out at: https://arduinojson.org/
 //
 // The book "Mastering ArduinoJson" contains a case study of a project that has
 // a complex configuration with nested members.
 // Contrary to this example, the project in the book uses the SPIFFS filesystem.
-// Please check it out at: https://arduinojson.org/book/
+// Learn more at https://arduinojson.org/book/
+// Use the coupon code TWENTY for a 20% discount ❤❤❤❤❤

examples/JsonGeneratorExample/JsonGeneratorExample.ino

@@ -70,12 +70,12 @@ void loop() {
 // See also
 // --------
 //
-// The website arduinojson.org contains the documentation for all the functions
+// https://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/
+// Learn more at https://arduinojson.org/book/
+// Use the coupon code TWENTY for a 20% discount ❤❤❤❤❤

examples/JsonHttpClient/JsonHttpClient.ino

@@ -100,13 +100,13 @@ void loop() {
 // See also
 // --------
 //
-// The website arduinojson.org contains the documentation for all the functions
+// https://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 deserialization
 // showing how to parse the response from Yahoo Weather. In the last chapter,
 // it shows how to parse the huge documents from OpenWeatherMap
 // and Weather Underground.
-// Please check it out at: https://arduinojson.org/book/
+// Learn more at https://arduinojson.org/book/
+// Use the coupon code TWENTY for a 20% discount ❤❤❤❤❤

examples/JsonParserExample/JsonParserExample.ino

@@ -67,12 +67,12 @@ void loop() {
 // See also
 // --------
 //
-// The website arduinojson.org contains the documentation for all the functions
+// https://arduinojson.org/ contains the documentation for all the functions
 // used above. It also includes an FAQ that will help you solve any
 // deserialization problem.
-// Please check it out at: https://arduinojson.org/
 //
 // The book "Mastering ArduinoJson" contains a tutorial on deserialization.
 // It begins with a simple example, like the one above, and then adds more
 // features like deserializing directly from a file or an HTTP request.
-// Please check it out at: https://arduinojson.org/book/
+// Learn more at https://arduinojson.org/book/
+// Use the coupon code TWENTY for a 20% discount ❤❤❤❤❤

examples/JsonServer/JsonServer.ino

@@ -98,12 +98,12 @@ void loop() {
 // See also
 // --------
 //
-// The website arduinojson.org contains the documentation for all the functions
+// https://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, then adds more features like serializing
 // directly to a file or an HTTP client.
-// Please check it out at: https://arduinojson.org/book/
+// Learn more at https://arduinojson.org/book/
+// Use the coupon code TWENTY for a 20% discount ❤❤❤❤❤

examples/JsonUdpBeacon/JsonUdpBeacon.ino

@@ -90,12 +90,12 @@ void loop() {
 // See also
 // --------
 //
-// The website arduinojson.org contains the documentation for all the functions
+// https://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, then adds more features like serializing
 // directly to a file or any stream.
-// Please check it out at: https://arduinojson.org/book/
+// Learn more at https://arduinojson.org/book/
+// Use the coupon code TWENTY for a 20% discount ❤❤❤❤❤

examples/ProgmemExample/ProgmemExample.ino

@@ -59,12 +59,12 @@ void loop() {
 // See also
 // --------
 //
-// The website arduinojson.org contains the documentation for all the functions
+// https://arduinojson.org/ contains the documentation for all the functions
 // used above. It also includes an FAQ that will help you solve any memory
 // problem.
-// Please check it out at: https://arduinojson.org/
 //
 // The book "Mastering ArduinoJson" contains a quick C++ course that explains
 // how your microcontroller stores strings in memory. It also tells why you
 // should not abuse Flash strings with ArduinoJson.
-// Please check it out at: https://arduinojson.org/book/
+// Learn more at https://arduinojson.org/book/
+// Use the coupon code TWENTY for a 20% discount ❤❤❤❤❤

examples/StringExample/StringExample.ino

@@ -64,11 +64,11 @@ void loop() {
 // See also
 // --------
 //
-// The website arduinojson.org contains the documentation for all the functions
+// https://arduinojson.org/ contains the documentation for all the functions
 // used above. It also includes an FAQ that will help you solve any problem.
-// Please check it out at: https://arduinojson.org/
 //
 // The book "Mastering ArduinoJson" contains a quick C++ course that explains
 // how your microcontroller stores strings in memory. On several occasions, it
 // shows how you can avoid String in your program.
-// Please check it out at: https://arduinojson.org/book/
+// Learn more at https://arduinojson.org/book/
+// Use the coupon code TWENTY for a 20% discount ❤❤❤❤❤