copyWithIn() with Array-like

Currently, following behavior.

```js
import { copyWithin } from "@immutable-array/copyWithin";
const arrayLike = { length: 5, 3: 1 };
let actual = copyWithin(arrayLike, 0, 3);
assert.deepStrictEqual(actual, [1, , , 1,]);
```

Native `Array#copyWithIn()` work following:

```js
[].copyWithin.call({length: 5, 3: 1}, 0, 3);
// {0: 1, 3: 1, length: 5}
```

It return just array-like object.

Is this no problem?

从 @immutable-array/copyWithin 入口点开始，使用提供的示例将其类数组行为与 Array#copyWithin.call 进行比较。确认预期结果是原始类数组对象还是返回的数组，然后检查是否有相关的回归测试，并在进行任何更改之前确定预期结果。

由索引模型根据 Issue 内容生成。