Hardware PWM on the Raspberry Pi 5 b

Since PWM is a little fraught with gotchas, this is mostly a message to future me-

(Note to self, rtfm - https://datasheets.raspberrypi.com/rp1/rp1-peripherals.pdf)

pin	a0	a3
GPIO19		PWM0_CHAN3
GPIO18		PWM0_CHAN2