Give Audio Coach notification when started

At present the Audio Coach doesn't give any notification until the first distance or time is complete. It could be minutes before finding out that a setting is wrong or not working, volume is muted, text-to-speech isn't not working. Heart rate is configured but not being actually measured, and is silently ignored. I know from experience there are many reasons.

My simple suggestion is to give an Audio Coach notification when started. It might say "distance zero km" or "time zero minutes" for example; whatever is configured. It would confirm all settings are good.

This idea would be very complementary to https://help.locusmap.eu/topic/38633-audio-coach-should-not-silently-ignore-missing-statistic for finding incorrect configurations.