Updated ci workflow with php7.4+

.gitlab-ci.yml

.php-cs-fixer.dist.php

README.md

composer.json

runtests.sh

src/AsciiCutSlugifier.php

src/AsciiTransliteratorSlugifier.php

src/SlugifierChain.php

src/SlugifierOptions.php

src/TrimSlugifier.php

test/AsciiCutSlugifierTest.php

test/AsciiTransliteratorSlugifierTest.php

test/LowercaseSlugifierTest.php

test/NoopSlugifierTest.php

test/SlugifierChainTest.php

test/SlugifierFactoryTest.php

test/SlugifierOptionsTest.php

test/TrimSlugifierTest.php

test/UppercaseSlugifierTest.php