webaudio package

[felixroos]

this package contains:

• clockworker: Web Worker that repeatedly runs timespan callback
• scheduler: uses clockworker to query pattern
• webaudio: basic webaudio pattern methods .osc .adsr and filter

This started as an experiment in the package-examples branch, trying to create a basic repl without tone.js.
In the future, we might replace the tone.js scheduling logic with this one.

Demo: https://tinyurl.id/oYCbj