It is now possible to send `mutable_content` option to Firebase which gets forwarded as `mutable-content` option for APNS. A link to official documentation is: https://firebase.google.com/docs/cloud-messaging/http-server-ref#mutable_content
* feat: check unused package update edganiukov/fcm to appleboy/go-fcm * update readme Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com> * update comment Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>