Function addEffect

addEffect(
    extra: PhiraExtra,
    shader: string,
    startBeat: number,
    endBeat: number,
    options?: CreateEffectOptions,
): number
Create a shader effect and add it to the extra.
Parameters
- extra: PhiraExtra
  PhiraExtra to modify in place.
- shader: string
  Shader name (built-in like "chromatic" or custom like "/myshader.glsl").
- startBeat: number
  Effect start beat.
- endBeat: number
  Effect end beat.
- options: CreateEffectOptions = {}
  Additional options.
Returns number
The index of the newly added effect.
Example
```
const extra = createExtra(120);
addEffect(extra, 'chromatic', 0, 8, {
  vars: { power: 0.02, sampleCount: 5 }
});
```
- Defined in extra.ts:169