Adding biquad filtering to `Signal`

[linclelinkpart5]

I'm working on a project that involves using biquad filtering on an audio signal. Right now I'm doing it by hand manually using map, but I was wondering if it would be helpful to have this be a first-class method on Signal? Perhaps a Signal::biquad(b0, b1, b2, a1, a2) that produces a new Signal?