Fixes multiple symfony deprecation warnings

[mikael-titinovskii]

Method "Symfony\Component\DependencyInjection\Extension\ExtensionInterface::load()" might add "void" as a native return type declaration in the future. Do the same in implementation "HtmlSanitizer\Bundle\DependencyInjection\HtmlSanitizerExtension" now to avoid errors or add an explicit @return annotation to suppress this message.

Method "Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface::process()" might add "void" as a native return type declaration in the future. Do the same in implementation "HtmlSanitizer\Bundle\DependencyInjection\CompilerPass\RegisterUserExtensionsCompilerPass" now to avoid errors or add an explicit @return annotation to suppress this message.

Method "Symfony\Component\Form\AbstractTypeExtension::configureOptions()" might add "void" as a native return type declaration in the future. Do the same in child class "HtmlSanitizer\Bundle\Form\TextTypeExtension" now to avoid errors or add an explicit @return annotation to suppress this message.

Method "Symfony\Component\Form\AbstractTypeExtension::buildForm()" might add "void" as a native return type declaration in the future. Do the same in child class "HtmlSanitizer\Bundle\Form\TextTypeExtension" now to avoid errors or add an explicit @return annotation to suppress this message.