Add driver for MCP9808 i2c temperature sensor

[gmonarque]

Hello,

I added basic support for the MCP9808 temp sensor. This includes:

• Temperature reading
• Precision configuration

I can't bother to implement the alerts feature, but if anyone really needs it let me know and I'll do it.

Datasheet: https://cdn-shop.adafruit.com/datasheets/MCP9808.pdf
Module: https://www.adafruit.com/product/1782

Thanks

[deadprogram]

Hello @gmonarque thank you very much for adding this sensor.

Could you please add it to the smoke tests? See https://github.com/tinygo-org/drivers/blob/dev/smoketest.sh#L132

Thanks!

[gmonarque]

@deadprogram Hello, I've updated the smoke tests as requested, I hope everything is good now! Thanks :)

[deadprogram]

Thank you very much @gmonarque now squash/merging!