[Feature]: Notify admin via Discord when added MQTT broker is offline beyond configured timeout

[MrAlders0n]

Platform: Other

Description:
custom MQTT broker offline status, notify admin via discord if added MQTT broker is offline for longer than set period

Discord: https://discord.com/channels/1463383723327356992/1523333798840897587/1546113663377739836

Submitted by: mxda. (Discord)