Merge pull request #9 from symfony2admingenerator/fix-nullable-php8.4

Fix nullable php8.4, remove old spaceless function

Drop PHP 8.1 support

Fix wrong reference in BaseBuilder

Mark class constants for Generator and Builder as non-final

Implement strict typing and some other PHP 8 features

Merge pull request #7 from tobias-93/master

Fix deprecated Twig function call for Twig 3 compatibility

Merge pull request #6 from tobias-93/master

Fix escaping of extensions, add extra filters for standard PHP functions

Merge pull request #5 from tobias-93/master

Update to allow Twig 3, switch to PSR-4

Twig 2.0 fix

Allow Twig 2.0