health check (ping maintainers in case of outage)

STUB

Value

• team-friendo wants to know when signalboost is down without having to check manually

Behavior

• ping signalboost support channel with HELP every minute (5 minutes?)
• if it ever doesn't respond send an alert to support channel admins

Implementation

• this will be a bit tricky b/c this checker will have to run in a separate container (maybe even server?) than the main app because it needs to both check if signald is down, but then use signald to message people if it is. hence use a separate signald instance for the sending of the checks and alerts than the mainline signald instance used in the app