show required options on usage

[Benjamin Fischer]

Discussed in #583

^{Originally posted by scarf005 April 9, 2023}
since they are always required, it'd be great for usage to also display required options.

example:

  Usage: COMMAND <id> --replace <type> --using <type>

  Description:

    replace contents of a JSON entry with another JSON entry with the same id.   
    this is useful for replacing mod content with vanilla content and vice versa.

  Options:

    -h, --help             - Show this help.                                 
    -l, --lint             - lint all json files after migration.            
    -r, --replace  <type>  - path to recursively search jsons.     (required)
    -u, --using    <type>  - path to recursively search jsons.     (required)
```</div>