Add TCA9548A drivers

[QuirkyCort]

This is a driver for the TCA9548A (I2C multiplexer). https://github.com/QuirkyCort/IoTy/blob/main/public/extensions/tca9548a.py

This is a really trivial driver, but I suppose it may be useful to some.

This driver was written for the IoTy project (...a web-based blocks to Python system, similar to BIPES), so it doesn't have it's own repository.