Support inverting level shifters

[your-friend-alice]

• Arduino board: Custom RP2040 (future revision will be SAMD21-based)
• arduino-cli version 1.0.3

I have made a custom RP2040 board, that uses a 1-transistor inverting level shifter to drive its onboard WS2812B chain. This is a nice arrangement as it's a very small footprint for very low cost. I've verified that the circuit works using a quick proof-of-concept where I just flipped all the side-set bits in the PIO code, but it would be useful to have support for this in a mainstream, user-friendly library that people are already familiar with. I'm thinking support could be added either through optional boolean constructor argument named invert, or a mutator method invert().

I'd be happy to contribute PRs, but since it would involve adding to the API I'd like input on what would best fit Adafruit's vision for the library.