Add support for Sensirion SHT31 sensor devices

[amotl]

Hi there,

at [1], we are discussing the current shortage on Bosch's BME and BMP sensors, started by @ClemensGruber. @wetterfrosch also stated at [2]:

Meteorologically, I've also been squinting more at Sensirion's SHTxx series lately.

In order to implement this for Terkin, we might want to look at those libraries by @mcauser and @kfricke:

• https://github.com/mcauser/micropython-sht31
• https://github.com/kfricke/micropython-sht31

With kind regards,
Andreas.

[1] https://community.hiveeyes.org/t/bme280-lieferengpass/4176
[2] https://community.hiveeyes.org/t/bme280-lieferengpass/4176/9