Create a entity that report the seconds proxy is out skull

**Is your feature request related to a problem? Please describe.**
Hello. Sometimes a proxy disconect or not reporting information. Tipically skull icon in bermuda.
This is a problem with a easy solution with a automation. Maybe reboot of esphome or reconect command in the wifi router.

**Describe the solution you'd like**
my proposal solution is a entity per each esphome with the seconds offline, or maybe a entity with on or off icon, or skull.
i dont know why but a entity per device that show the offline proxy in bermuda

thanks a lot for your work. this is a very interesting project!!!!