Update Wiki in regards to using an ESP8266

[systobe]

First of all, thanks for your work! Great job which I definitely wouldn't be able to do.

I had ESP8266 laying around and wanted to use it for that purpose. There are some remarks which took me quite some time to figure out. You may add them to the wiki for other people to see.

• Not related to ESP8266, but I thought the connection from DE and RE to a GPIO is not needed because I don't want to send data and I omitted it. It turned out, that it is not working without it. So maybe mention that in a side note :)

• I used GPIO 4 and 5 for the RS485 to TTL module.

  tx_pin: 4 # goes to D1
  rx_pin: 5 # goes to R0

• Apparently another board config is needed:

  esp8266:
    board: esp12e

• With the master firmware version 1.22 it is not possible to receive data via RS485 from the inverter. I got a confirmation from the support about that. They plan to make it possible again in the future. You can ask them to downgrade the firmware.

• This setup can also be used for other home automation systems like openHAB. Just use the mqtt function of esphome.