docs(custom-decorators) update where decorators can be used

Author: lucasfloriani

content/custom-decorators.md

@@ -5,7 +5,7 @@ Nest is built around a language feature called **decorators**. Decorators are a
 <blockquote class="external">
   An ES2016 decorator is an expression which returns a function and can take a target, name and property descriptor as arguments.
   You apply it by prefixing the decorator with an <code>@</code> character and placing this at the very top of what
-  you are trying to decorate. Decorators can be defined for either a class or a property.
+  you are trying to decorate. Decorators can be defined for either a class, a method or a property.
 </blockquote>
 
 #### Param decorators