Ability to repeat alarms in emergency state

[davidsanner]

Currently only notification state transition results in an audio alert.

For current alarms in 'emergency' state the ability to have the audio repeated (user set rate/delay) seems critical for emergencies like anchor dragging, engine overheating, etc.

Apps like Freeboard-SK & WilhelmSK manage these alarm states and repeat the audio alert as well as provide the ability to mute them but need to be running. For signalk-audio-notifications, having a simple user set repeat rate/delay for emergency states would provide a valuable default use case, especially when these front end apps are not running. Thanks.