add midi, note, and freq unit conversions

[ogbabydiesal]

for reference

freqToMidi()
midiToFreq()

[kemkartanya]

@ogbabydiesal I can do this

[kemkartanya]

where these to be added @ogbabydiesal

[ogbabydiesal]

@kemkartanya lets chat about this here - anyone else want to weigh in? i personally think it would be super cool to have this - we want to make sure that we are only adding things which would be useful to have in a beginner friendly library and we aren't adding features which might be unnecessary. part of the redesign process was to trim the excess - but I feel like I thought of some good reasons to have this but can't remember them now haha

[ogbabydiesal]

hi @kemkartanya wondering if you would be willing to work on this? was thinking it would be great to be able to do something like this:

osc = new p5.Oscillator('C#4')

or

osc.freq('F3')

setting pitch with midi might look like this

osc.freq(midiToFreq(60))

and

let coolFrequency = midiToFreq(60)
osc.freq(coolFreqency)

with

frequencyToMidi working in a similar fashion to midiToFreq