v2.2.0

• Add lowpass, highpass, bandpass filters (effect) — biquad + Butterworth cascade, configurable order
• Add notch filter (effect) — band-reject via RBJ biquad
• Split shelving into separate lowShelf and highShelf exports (eq) — one concern per file
• Add TypeScript declarations for all new and previously untyped filters (lowpass, highpass, bandpass, notch, lowShelf, highShelf, baxandall, tilt)
• Add SVG plots for lowpass, highpass, bandpass, notch, lowshelf, highshelf
• Remove dangling plot references to unimplemented filters (envelope, slewLimiter, noiseShaping, phaser, flanger, chorus, wah)
• Add tests for lowpass, highpass, bandpass (9 new tests, 107 total)

Breaking: import { lowShelf, highShelf } from 'audio-filter/eq' now works the same way but the internal file changed from shelving.js to lowshelf.js / highshelf.js. Direct deep imports to eq/shelving.js will break.

Full Changelog: v2.1.0...v2.2.0