Fix the handling of the html_sanitizer service for the main serializer (

#10)

It should be an alias of the named service, instead of being a separate sanitizer instance using the same definition.

src/DependencyInjection/HtmlSanitizerExtension.php

@@ -72,7 +72,7 @@ private function registerSanitizers(ContainerBuilder $container, array $sanitize
 
             if ($name === $default) {
                 $container->setAlias(SanitizerInterface::class, 'html_sanitizer.'.$name);
-                $container->setDefinition('html_sanitizer', $definition);
+                $container->setAlias('html_sanitizer', 'html_sanitizer.'.$name);
             }
 
             $refMap[$name] = new ServiceClosureArgument(new Reference('html_sanitizer.'.$name));