Typescript Declarations

Seeing as the last commit was 9+ years ago I don't expect typings to be added to the module, but if anyone else needs them this is the declaration file I've used:

```typescript
declare module "perlin-noise" {
type PerlinNoiseOptions = {
octaveCount?: number;
amplitude?: number;
persistence?: number;
};
declare function generatePerlinNoise(width: number, height: number, options?: PerlinNoiseOptions): number[];
declare function generateWhiteNoise(width: number, height: number): number[];

export {
PerlinNoiseOptions,
generateWhiteNoise,
generatePerlinNoise,
};
}
```