Here's how you can implement chunk function in TypeScript:

```ts
export function chunk<T>(items: readonly T[], size: number): T[][] {
    if (size < 1) {
        throw new Error('Size must be a positive integer');
    }
    const result = [];
    for (let i = 0; i < items.length; i += size) {
        result.push(items.slice(i, i + size));
    }
    return result;
}
```