2.4.0

Various updates by @reedy (thanks) 👍🏻

• Use GitHub actions for CI; fixes #30
• Test on PHP 8.1-8.5; fixes #29
• Drop support for PHP versions < 8.0; fixes #35
• Remove dupliate phpunit.xml; fixes #32
• Remove manual autoload.php; fixes #33
• Remove version from composer.json; see https://getcomposer.org/doc/04-schema.md#version

What's Changed

• .gitattributes: Remove composer.travis.json by @reedy in #31
• Various updates by @reedy in #34

Full Changelog: 2.3.0...2.4.0