feat: addex langfuse_example module - but not fully cooked yet

.gitignore

modules/langfuse_example/README.md

modules/langfuse_example/composer.json

modules/langfuse_example/css/demo.css

modules/langfuse_example/css/langfuse_example.css

modules/langfuse_example/langfuse_example.info.yml

modules/langfuse_example/langfuse_example.libraries.yml

modules/langfuse_example/langfuse_example.links.menu.yml

modules/langfuse_example/langfuse_example.links.task.yml

modules/langfuse_example/langfuse_example.module

modules/langfuse_example/langfuse_example.routing.yml

modules/langfuse_example/langfuse_example.yml

modules/langfuse_example/src/Form/OpenAiDemoForm.php

modules/langfuse_example/src/Form/OpenAiSettingsForm.php