[pigeon]Add hellohuanlin to pigeon iOS for code reviews (flutter#6333)

So that I get notified for code reviews. I am mainly interested in Swift codegen. 

*Replace this paragraph with a description of what this PR is changing or adding, and why. Consider including before/after screenshots.*

*List which issues are fixed by this PR. You must list at least one issue.*

*If you had to change anything in the [flutter/tests] repo, include a link to the migration guide as per the [breaking change policy].*

Author: hellohuanlin

CODEOWNERS

@@ -88,8 +88,9 @@ packages/google_sign_in/google_sign_in_ios/**            @vashworth
 packages/image_picker/image_picker_ios/**                @vashworth
 packages/in_app_purchase/in_app_purchase_storekit/**     @louisehsu
 packages/ios_platform_images/**                          @jmagman
-packages/local_auth/local_auth_darwin/**                    @louisehsu
+packages/local_auth/local_auth_darwin/**                 @louisehsu
 packages/path_provider/path_provider_foundation/**       @jmagman
+packages/pigeon/**/ios/**/*                              @hellohuanlin
 packages/pointer_interceptor/pointer_interceptor_ios/**  @ditman
 packages/quick_actions/quick_actions_ios/**              @hellohuanlin
 packages/shared_preferences/shared_preferences_foundation/**  @tarrinneal