* if the `action` is `add`, adds an emoji named `shortcode` to the pack `pack_name`,
that means that the emoji file needs to be uploaded with the request
(thus requiring it to be a multipart request) and be named `file`.
* if the `action` is `add`, adds an emoji named `shortcode` to the pack `pack_name`,
that means that the emoji file needs to be uploaded with the request
(thus requiring it to be a multipart request) and be named `file`.