Function floatingTextAlpha

floatingTextAlpha(t: number, hold: number): number
Opacity at normalised progress t (0 to 1), with hold of that life spent at full opacity.

Pulled out of the container and exported so the curve is checked as arithmetic rather than through a rendered label - Label needs a DOM to measure text, and the split between what a thing is and how it is drawn is the same one Level/TileMap and ParticleEmitter's textureless mode already draw.
Parameters
- t: number
- hold: number
Returns number
Example
```
import { floatingTextAlpha } from '@datamoc/mw_games/two-d/ui';
console.log(floatingTextAlpha(0.75, 0.5)); // 0.5
```
- Defined in src/two-d/ui/FloatingText.ts:38