Change Notification Sound

Hi, i’m using your plugin on my wordpress blog to send push notifications (through firebase) to my iOS app.

Now, i’d like to change the default sound and i know i’ve to include the audio file within my app project but i think i also have to edit your plugin to add the filename.extension somewhere

is that right?

something like:

{
    "to":"myToken",
    "aps":{
        "title":"new message",
        "body":"Hello World!",
        "sound":"tweet_sent.caf",
        "badge": 3
    }
}

Where and What i have to write to edit your plugin to enable a new push notification sound?