Add mask for Laravel Str helper

StrMask.php

<?php
// abcde -> a*e
Str::macro('mask', function ($subject, $maxlength = 5, $mask_symbol = '*'): string {
    $subject = mb_substr($subject, 0, $maxlength);
    $length = mb_strlen($subject, 'utf-8');

    if ($length < 2) {
        return $subject;
    }

    $firstStr = mb_substr($subject, 0, 1, 'UTF-8');
    $lastStr = mb_substr($subject, -1, 1, 'UTF-8');

    return $firstStr.$mask_symbol.$lastStr;
});