Pads the end of a string w/ repeated spaces|substrings
string(string): input string[length](number): length of the padded portion *(default0)*[substr](string): substring to apply *(default ' ')*
(string): the input padded w/ spaces|substrings
// if no `substr` is provided, it pads the string w/ spaces
const result = strings.padEnd('abcabc', 9);
console.log(result);
> abcabc