Add support for PCA9547D devices

[Pyetrek]

Hello, I have a project where I am using the PCA9547D mux with a couple nau7802s. Turns out the PCA9547's control register works a bit differently, so I created a couple of subclasses to handle that. I hope this is useful to others!

[FoamyGuy]

I think typically we would want something like this to be a separate library. That way on devices with limited RAM we can minimize the amount of unused code that is loaded into memory for any given project. The separate library can list this one as a requirement and still extend the superclass from here.

We also have some infrastructure pieces that assume scripts in the examples/ directory will begin with the same base name as the library they belong to. i.e. for Adafruit_CircuitPython_TCA9548A all of the examples should begin with the prefix tca9548a_ Though I do see there are already some examples with different names existing there now.

[Pyetrek]

Hi @FoamyGuy, thanks for the response. I can setup a new library with this code included. Is adafruit interested in owning said repository or will it remain 3rd party?

[FoamyGuy]

@Pyetrek Usually we would only own the library if it supports a piece of Adafruit hardware. Other wise it can be added to the Community Bundle which is published alongside the Adafruit one and libraries within it are available with tooling like circup.

You could ask in the #circuitpython-dev channel on discord, or during the "in the weeds" section of the weekly meeting on a Monday if you'd like to see if anyone has other ideas for how to publish.