When I try to do http request this with Angular I’m getting CORS errors, because custom headers presents in request, Angular make OPTIONS request and getting CORS error.
So, custom header of course is Client-ID. Try to execute this http request in your Angular code and see what happen.
GET /chat/emoticons is old and shouldn’t be used anymore. I’m surprised it hasn’t been removed yet or at least marked as deprecated in the docs. You will want to migrate to GET /chat/emoticon_images.