Update custom-decorators.md

Author: kamilmysliwiec

content/custom-decorators.md

@@ -161,17 +161,19 @@ Nest treats custom param decorators in the same fashion as the built-in ones (`@
 ```typescript
 @@filename()
 @Get()
-async findOne(@User(new ValidationPipe()) user: UserEntity) {
+async findOne(@User(new ValidationPipe({ validateCustomDecorators: true })) user: UserEntity) {
   console.log(user);
 }
 @@switch
 @Get()
-@Bind(User(new ValidationPipe()))
+@Bind(User(new ValidationPipe({ validateCustomDecorators: true })))
 async findOne(user) {
   console.log(user);
 }
 ```
 
+> info **Hint** Note that `validateCustomDecorators` option must be set to true. `ValidationPipe` does not validate arguments annotated with the custom decorators by default.
+
 #### Decorator composition
 
 Nest provides a helper method to compose multiple decorators. For example, suppose you want to combine all decorators related to authentication into a single decorator. This could be done with the following construction: