feat: basic themes for event sites

src/Twig/AppExtension.php

@@ -30,6 +30,7 @@ class AppExtension extends AbstractExtension
             new TwigFunction('is_static_text', [AppRuntime::class, 'isStaticText']),
             new TwigFunction('is_hidden', [AppRuntime::class, 'isHidden']),
             new TwigFunction('collect_invalid_field_labels', [AppRuntime::class, 'collectInvalidFieldLabels']),
+            new TwigFunction('booking_theme', [AppRuntime::class, 'getBookingTheme']),
         ];
     }
 }