Add suport: Seeed Grove Multichannel Gas Sensor v2 (CO, NO2, C2H5CH and VOC)

**Describe the problem you have/What new integration you would like**

It would be nice to add support for this multi-gas sensor from Seeed Studios with I2C interface.
Four fully independent sensor elements on one package, ability to detect Carbon monoxide (CO), Nitrogen dioxide (NO2), Ethyl alcohol (C2H5CH) and Volatile Organic Compounds (VOC).

**Please describe your use case for this integration and alternatives you've tried:**

This multi-gas sensor would be a very nice addition.

**Additional context**

Link to the sensor : https://wiki.seeedstudio.com/Grove-Multichannel-Gas-Sensor-V2/
https://www.seeedstudio.com/Grove-Multichannel-Gas-Sensor-v2-p-4569.html
https://eu.mouser.com/ProductDetail/713-101020820

Library: https://github.com/Seeed-Studio/Seeed_Multichannel_Gas_Sensor/archive/master.zip

Start with the linked Seeed wiki, product pages, and Seeed_Multichannel_Gas_Sensor library to understand the I2C protocol and the four sensor readings. Then identify the project's existing sensor integration entry points; done means the Grove Multichannel Gas Sensor v2 is supported and can expose CO, NO2, C2H5CH, and VOC measurements.

Written by the indexing model from the issue text.