Function longestWord

longestWord(str: string): string | string[]
Finds the longest word(s) in a string.
Parameters
- str: string
  The input string.
Returns string | string[]
The longest word as a string, or an array of tied words.
Remarks
- If only one longest word exists, returns it as a string.
- If multiple longest words have the same length, returns them as an array.
- Returns an empty string if there are no words.
Example
```
longestWord("js utils kit");              // "utils"
longestWord("short   longerword   mid"); // "longerword"
longestWord("hello");                    // "hello"
longestWord("");                         // ""
```
- Defined in src/string/fn.ts:260