add code tabs in num14.

Author: benluo

_overviews/scala3-book/taste-contextual-abstractions.md

@@ -19,11 +19,15 @@ Those parameters are called _Context Parameters_ because they are inferred by th
 
 For instance, consider a program that sorts a list of addresses by two criteria: the city name and then street name.
 
+{% tabs contextual_1 class=tabs-scala-version %}
+{% tab 'Scala 2 and 3' for=contextual_1 %}
 ```scala
 val addresses: List[Address] = ...
 
 addresses.sortBy(address => (address.city, address.street))
 ```
+{% endtab %}
+{% endtabs %}
 
 The `sortBy` method takes a function that returns, for every address, the value to compare it with the other addresses.
 In this case, we pass a function that returns a pair containing the city name and the street name.
@@ -39,9 +43,13 @@ It is convenient to omit it because we know `String`s are generally compared usi
 
 However, it is also possible to pass it explicitly:
 
+{% tabs contextual_2 class=tabs-scala-version %}
+{% tab 'Scala 2 and 3' for=contextual_2 %}
 ```scala
 addresses.sortBy(address => (address.city, address.street))(using Ordering.Tuple2(Ordering.String, Ordering.String))
 ```
+{% endtab %}
+{% endtabs %}
 
 In this case, the `Ordering.Tuple2(Ordering.String, Ordering.String)` instance is exactly the one that is otherwise inferred by the compiler.
 In other words both examples produce the same program.
@@ -51,7 +59,5 @@ They help developers write pieces of code that are extensible and concise at the
 
 For more details, see the [Contextual Abstractions chapter][contextual] of this book, and also the [Reference documentation][reference].
 
-
-
 [contextual]: {% link _overviews/scala3-book/ca-contextual-abstractions-intro.md %}
 [reference]: {{ site.scala3ref }}/overview.html