PHP 7.3 Support

Hello and thanks for your great plugin!

I recently ran a site scan using the PHP Compatibility Checker plugin and received the following warning:

FILE: ***/wp-content/plugins/autoptimize/classes/external/php/jsmin.php
-----------------------------------------------------------------------------------------------------
FOUND 0 ERRORS AND 1 WARNING AFFECTING 1 LINE
-----------------------------------------------------------------------------------------------------
 109 | WARNING | INI directive 'mbstring.func_overload' is deprecated since PHP 7.2
-----------------------------------------------------------------------------------------------------

What version of PHP is safest to utilize and ensure complete functionality of your plugin? Do you have any plans to address this concern so that users can update to 7.3 without issue?

Thank you!