Added missing code tag as pointed out in #2371

See #2371

spec/introduction.md

@@ -581,7 +581,7 @@ public class Point
 ```
 Instances of classes are created using the `new` operator, which allocates memory for a new instance, invokes a constructor to initialize the instance, and returns a reference to the instance. The following statements create two `Point` objects and store references to those objects in two variables:
 
-```
+```csharp
 Point p1 = new Point(0, 0);
 Point p2 = new Point(10, 20);
 ```