Function splitByLength

splitByLength(source: null | string, length: number): readonly string[]
Splits a string into length-size chunks.

If length is greater than the length of source, a single element array is returned with source. The final array element may be smaller if we ran out of characters.
```
splitByLength(`hello there`, 2);
// Yields:
// [`he`, `ll`, `o `, `th`, `er`, `e`]
```
Parameters
- source: null | string
  Source string
- length: number
  Length of each chunk
Returns readonly string[]