Maintenance Work

[razvanphp]

• [x] Add github actions, fix phpunit tests
• [x] Repacked the test p12 cert so it works with openssl3 in PHP 8.2, see https://www.php.net/manual/en/function.openssl-pkcs12-read.php#128992
• [x] Remove unused circleci, ~scrutinizer~ and travis configs
• [ ] Add PHP_CodeSniffer (phpcs) config for PSR12 standard, fix all errors and add it as github actions step
• [ ] Add test coverage badge somewhere