Add device support for Shelly Pro 2 PM

[ChristianWaechter]

I bought a Shelly Pro 2 PM with power metering as I assumed that is supported by ESPhome out of the box. But as I now try to build a configuration, I saw that there is nearly no information available on this device.

The Shelly Pro 2 (without PM) has been added recently: #5866

I would assume that the Shelly Pro 2 PM is rather similar so I wonder if it might be already working but the configuration is not yet on the esphome page? In case it is required, I can try to open my Shelly Pro 2 PM and provide images from the inside.

Thanks in advance :)