Add LED driver PCA9633

**Describe the problem you have/What new integration you would like**

Requesting support for the NXP PCA9633 four channel LED driver. It is much simpiler device than the PCA9685 and only has four outputs rather than 16. Also it is only 8 bit instead of 12 bit.

The datasheet can be found here:
https://www.nxp.com/products/analog/interfaces/ic-bus/ic-led-controllers/4-bit-fm-plus-ic-bus-led-driver:PCA9633

**Please describe your use case for this integration and alternatives you've tried:**

I am trying to reverse engineer the existing PCA9685 module but not having much luck yet.

**Additional context**

I have written a simple Arduino library for the chip here. It works on ESP8266 and some Arduino boards.

https://github.com/gordonthree/pca9633