PWMOut class for ESP32SPI

[brentru]

This pull request adds PWMOut-like support for esp objects via the set_analog_write method in adafruit_esp32spi.py.

Note: The WiFiNINA firmware implements an analogWrite. Setting the frequency property of a PWMOut object with this class is currently not supported.

Implementation Example

# Create the ESP32 Object
esp = adafruit_esp32spi.ESP_SPIcontrol(spi, esp32_cs, esp32_ready, esp32_reset)

# Import PWMOut class
import adafruit_esp32spi.PWMOut

# Create an ESP32SPI PWMOut Object
led = adafruit_esp32spi.PWMOut.PWMOut(esp, 25)

while True:
    for i in range(100):
        # PWM LED up and down
        if i < 50:
            led.duty_cycle = int(i * 2 * 65535 / 100)  # Up
        else:
            led.duty_cycle = 65535 - int((i - 50) * 2 * 65535 / 100)  # Down
        time.sleep(0.01)

Tested on a Feather M4 w/AirLift FeatherWing