Add .php8 files to phar file

vendor/symfony/polyfill-mbstring/Resources/mb_convert_variables.php8

Author: Naktibalda

RoboFile.php

@@ -667,6 +667,7 @@ private function packPhar($pharFileName)
         $finder = Finder::create()->files()
             ->ignoreVCS(true)
             ->name('*.php')
+            ->name('*.php8')
             ->name('*.css')
             ->name('*.png')
             ->name('*.js')