Add concentric circles zoom sketch

[msfeldstein]

Adds concentric-zoom.js — an animated canvas-sketch that draws concentric circles continuously zooming inward, creating a hypnotic tunnel effect.

How it works:

• 24 primary circles expand outward in a looping cycle, giving the illusion of zooming into the center
• Each circle has a subtle wobble and slight elliptical distortion that evolves over time
• 3 additional ghost ring layers at different speeds add depth
• Uses a warm color palette (#264653, #2a9d8f, #e9c46a, #f4a261, #e76f51, etc.)
• Alpha fades circles in/out smoothly as they scale

Run it:

npx canvas-sketch-cli concentric-zoom.js --open