WebGL: add parameter count validation to directionalLight() and pointLight()

[MASTERsj01]

Increasing access

Both directionalLight() and pointLight() in src/webgl/light.js have a @TODO: check parameters number comment but no actual validation. Invalid argument counts silently cause unexpected behavior instead of showing a helpful error.

These functions accept 2, 4, or 6 arguments but currently don't validate the count.

I have a PR ready for this.

Most appropriate sub-area of p5.js?

• Accessibility
• Color
• Core/Environment/Rendering
• Data
• DOM
• Events
• Image
• IO
• Math
• Typography
• Utilities
• WebGL
• Build process
• Unit testing
• Internationalization
• Friendly errors
• Other (specify if possible)

Feature enhancement details

Both directionalLight() and pointLight() in src/webgl/light.js have a @TODO: check parameters number comment (lines 644 and 920) but no actual validation. These functions accept 2, 4, or 6 arguments but currently don't check the count — invalid argument counts silently cause unexpected behavior instead of showing a helpful error.