Add missing to

Author: samdark

spec.md

@@ -300,7 +300,7 @@ there are no arguments passed to the constructor. For example:
 new Foo();
 ```
 
-If class contains no additional declarations (such as an exception that exists only extend another exception with a new type),
+If class contains no additional declarations (such as an exception that exists only to extend another exception with a new type),
 then the body of the class SHOULD be abbreviated as `{}` and placed on the same line as the previous symbol,
 separated by a space. For example: