Add SGP40 sensor support

[thetic]

Add support for the SGP40 Sensor for VOC measurement. This sensor needs a temp + humidity sensor to work optimally, but will assume 25°C and 50% humidity if not provided. This was adapted from the Nevermore project. This code was written by @meteyou and submitted to Klipper, but it is not Python2 compatible. Support has already been added to Mainsail.

[temperature_sensor BME_OUT]
sensor_type: BME280
i2c_address: 118
i2c_mcu: pico
i2c_bus: i2c1e
i2c_speed: 400000

[temperature_sensor SGP_OUT]
sensor_type: SGP40
i2c_mcu: pico
i2c_bus: i2c1e
ref_temp_sensor: bme280 BME_OUT
ref_humidity_sensor: bme280 BME_OUT

Checklist

• pr title makes sense
• squashed to 1 commit
• added a test case if possible
• if new feature, added to the readme
• ci is happy and green

[meteyou]

@thetic Thx for creating the PR in Kalico, but pls wait a little bit. I will refactoring this module, that i doesnt need a pip dependencies. I will update the Klipper PR as soon as possible (at least between christmas and new year).