el.phasor([props], rate, reset)
Outputs a ramp from 0 to 1 at the given rate. Expects two children, the first providing
the ramp rate in
hz, the second a pulse train for resetting the phasor.
The phasor will snap its phase back to 0 on each rising edge of the reset pulse train. To
avoid a reset you can simply pass a constant value
0 for the second argument.