Add compatibility with ESP32 GPIO RGB LEDs

[brentru]

This pull request adds:

• RGBLED support for using an ESP_SPIControl object, esp, provided three RGB LED pins.
• color setter method no longer handles PWM, only color conversion and integer scaling.
  • _write_color method added to support multiple types of PWMOut methods and simplify color() setter.
• Usage example for ESP32-connected RGBLEDs

Usage Example

import board
import adafruit_rgbled
from adafruit_esp32spi import adafruit_esp32spi

# Create ESP Object
esp32_cs = DigitalInOut(board.D13)
esp32_ready = DigitalInOut(board.D11)
esp32_reset = DigitalInOut(board.D12)
spi = busio.SPI(board.SCK, board.MOSI, board.MISO)

esp = adafruit_esp32spi.ESP_SPIcontrol(spi, esp32_cs, esp32_ready, esp32_reset)

with adafruit_rgbled.RGBLED(25, 26, 27, esp) as rgb_led:
    rgb_led.color = (0, 255, 0)

This pull request has been tested with: a pin-based RGB LED, PCA9685 (PWMOut object), and a RGB LED connected to an ESP32 (AirLift FeatherWing)

[ladyada]

i think maybe better to have ESPSPI provide the PWM objects then pass em in?

[brentru]

@ladyada I don't think ESP32SPI creates PWM objects, though. It sets a pin's mode (https://github.com/adafruit/Adafruit_CircuitPython_ESP32SPI/blob/master/adafruit_esp32spi/adafruit_esp32spi.py#L629) and can "write" to the pin (https://github.com/adafruit/Adafruit_CircuitPython_ESP32SPI/blob/master/adafruit_esp32spi/adafruit_esp32spi.py#L659).

[ladyada]

ok then update espspi to create PWMouts :)

[brentru]

This PR is no longer required as the pull request for adding a PWMOut class in ESP32SPI (adafruit/Adafruit_CircuitPython_ESP32SPI#52) creates PWMOut objects, and they're already handled in this library. Tested on Feather M4 + AirLift FeatherWing.

Closing out...