Feature request: Add TipRingVoltage of Line Port

[rvendrame]

Hi @dshokouhi , it seems you were the last one to work on this integration.

Here in my country we usually have fuses on the land lines, as we have a high incidence of lightning events every year.

So, from time to time, a fuse blows. The only way I found to identify (and notify) it was to check the "TipRingVoltage" status of the Line port at my Obi100. This was working like a charm in my previous controller (Vera), and it is my last open topic in my newly Home Assistant.

I tried to create a scrape sensor, but due my beginner skills I could not achieve it.

As the Obihai integration is working flawlessly since I installed that, I wondered if is it too complicate to expose the "TipRingVoltage" from the Obi device, as a sensor in HA. In that way I could create an automation that notifies me once the Voltage drops to zero for many minutes.

I might try a pull request, depending on your answer + guidance.

Thanks
Ricardo