added 8.0 into required php versions

[ayhandoslu]

The error below occurs on composer require, update, etc. on PHP 8 versioned system;

Your requirements could not be resolved to an installable set of packages.

Problem 1

• ardakilic/mutlucell is locked to version 5.1.0 and an update of this package was not requested.
• ardakilic/mutlucell 5.1.0 requires php ^7.3 -> your php version (8.0.1) does not satisfy that requirement.

Installation failed, reverting ./composer.json and ./composer.lock to their original content.

[Ardakilic]

Thank you! Indeed you're correct! I'll release a new version soon 👍