### arrayToCSV

Converts a 2D array to a comma-separated values (CSV) string.

Use `Array.prototype.map()` and `Array.prototype.join(delimiter)` to combine individual 1D arrays (rows) into strings.
Use `Array.prototype.join('\n')` to combine all rows into a CSV string, separating each row with a newline.
Omit the second argument, `delimiter`, to use a default delimiter of `,`.

```js
const arrayToCSV = (arr, delimiter = ',') =>
  arr.map(v => v.map(x => `"${x}"`).join(delimiter)).join('\n');
```

```js
arrayToCSV([['a', 'b'], ['c', 'd']]); // '"a","b"\n"c","d"'
arrayToCSV([['a', 'b'], ['c', 'd']], ';'); // '"a";"b"\n"c";"d"'
```
