update to master fork

Took a while to figure out an update. Need to use notificationChannel
for a sound. Have created an app specific notification channel ID as
well as a sound specific channel name. You apparently can’t update a
notification channel after its created, using default channel etc just
meant you used the system default and couldn’t change it.

Oreo requires use of a notification channel. Once a channel is created,
it can’t be modified (could be deleted but that’s unverified as a good
idea).
Consequently you need to create a channel for your app plus sound
combination and then use that.