bNoise v0.3

Added drag-and-drop `.noiseplugin` loading with `config.json` and `index.js` plugin archives.

Plugin instrument styles now appear in the existing instrument popup alongside built-in presets.

Plugins can use bNoise audio helpers or provide custom play hooks for leads, basses, pads, arps, and drums.

Added example plugin source folders and ready-to-drag `.noiseplugin` files in `examples/noiseplugins`.