Function center

center(text?, width?, placeholder?): string | undefined | null
Returns a string that centers the given text using placeholder
Parameters
- Optionaltext: null | string
  the text to inspect
- width: number = -1
  the max width of the expected string
- placeholder: string = ' '
  the placeholder to pad
Returns string | undefined | null
a string that centers the given text using placeholder
Example
```
center('foobar', -1);    // 'foobar'
center('foobar', 0);    // ''
center('foobar', 3);    // 'foobar'
center('foobar', 7);    // 'foobar '
center('foobar', 10);    // '  foobar  '
```