Add code tabs for _tour/case-classes (#2533)

* Add code tabs for _tour/case-classes

* Update _tour/case-classes.md

Co-authored-by: Jamie Thompson <[email protected]>

* Update _tour/case-classes.md

Co-authored-by: Jamie Thompson <[email protected]>

* Update case-classes.md

Co-authored-by: Jamie Thompson <[email protected]>

Author: flomebul

_tour/case-classes.md

@@ -15,36 +15,64 @@ Case classes are like regular classes with a few key differences which we will g
 
 ## Defining a case class
 A minimal case class requires the keywords `case class`, an identifier, and a parameter list (which may be empty):
+
+{% tabs case-classe_Book %}
+
+{% tab 'Scala 2 and 3' for=case-classe_Book %}
 ```scala mdoc
 case class Book(isbn: String)
 
 val frankenstein = Book("978-0486282114")
 ```
+{% endtab %}
+
+{% endtabs %}
+
 Notice how the keyword `new` was not used to instantiate the `Book` case class. This is because case classes have an `apply` method by default which takes care of object construction.
 
 When you create a case class with parameters, the parameters are public `val`s.
+
+{% tabs case-classe_Message_define %}
+
+{% tab 'Scala 2 and 3' for=case-classe_Message_define %}
 ```
 case class Message(sender: String, recipient: String, body: String)
 val message1 = Message("[email protected]", "[email protected]", "Ça va ?")
 
 println(message1.sender)  // prints [email protected]
 message1.sender = "[email protected]"  // this line does not compile
 ```
+{% endtab %}
+
+{% endtabs %}
+
 You can't reassign `message1.sender` because it is a `val` (i.e. immutable). It is possible to use `var`s in case classes but this is discouraged.
 
 ## Comparison
 Instances of case classes are compared by structure and not by reference:
+
+{% tabs case-classe_Message_compare %}
+
+{% tab 'Scala 2 and 3' for=case-classe_Message_compare %}
 ```scala mdoc
 case class Message(sender: String, recipient: String, body: String)
 
 val message2 = Message("[email protected]", "[email protected]", "Com va?")
 val message3 = Message("[email protected]", "[email protected]", "Com va?")
 val messagesAreTheSame = message2 == message3  // true
 ```
+{% endtab %}
+
+{% endtabs %}
+
 Even though `message2` and `message3` refer to different objects, the value of each object is equal.
 
 ## Copying
 You can create a (shallow) copy of an instance of a case class simply by using the `copy` method. You can optionally change the constructor arguments.
+
+{% tabs case-classe_Message_copy %}
+
+{% tab 'Scala 2 and 3' for=case-classe_Message_copy %}
 ```scala mdoc:nest
 case class Message(sender: String, recipient: String, body: String)
 val message4 = Message("[email protected]", "[email protected]", "Me zo o komz gant ma amezeg")
@@ -53,6 +81,10 @@ message5.sender  // [email protected]
 message5.recipient // [email protected]
 message5.body  // "Me zo o komz gant ma amezeg"
 ```
+{% endtab %}
+
+{% endtabs %}
+
 The recipient of `message4` is used as the sender of `message5` but the `body` of `message4` was copied directly.
 
 ## More resources