Function createLightingBit

createLightingBit(opts: CreateLightingBitOptions): ShaderBit
Advanced
Builds a lighting ShaderBit around the shading math in opts

Call it once at module scope and list the bit in a material's bitsGpu and bitsGl. CreateLightingBitOptions says what each snippet can read.
Parameters
- opts: CreateLightingBitOptions
  The lighting model's snippets and metadata
Returns ShaderBit
The composed lighting bit
Example: A diffuse-only Lambert model
```
export const lambertLightingBit = createLightingBit({
  name: 'lambertLighting',

  preLighting: {
    gpu: 'var directLight = vec3<f32>(0.0);',
    gl:  'vec3 directLight = vec3(0.0);',
  },

  perLight: {
    gpu: 'directLight += albedo * light.color * nDotL * attenuation * shadow;',
    gl:  'directLight += albedo * light.color * nDotL * attenuation * shadow;',
  },

  postLighting: {
    gpu: 'finalColor = directLight;',
    gl:  'finalColor = directLight;',
  },
});
```
The PBR material's Cook-Torrance lighting and the toon material's toonLightingBit are built the same way.