Update swagger.md

Author: kamilmysliwiec

content/recipes/swagger.md

@@ -339,6 +339,7 @@ pet: Cat | Dog;
 ```
 
 If you want to define a polymorphic array (i.e., an array whose members span multiple schemas), you should use a raw definition (see above) to define your type by hand.
+
 ```typescript
 type Pet = Cat | Dog;