Add Dify to Ruff users (astral-sh#12593)

## Summary

<!-- What's the purpose of the change? What does it do, and why? -->
- Add the popular LLM Ops project Dify to the user list in Readme, as
Dify introduced Ruff for lining since Feb 2024 in
langgenius/dify#2366

README.md

@@ -424,6 +424,7 @@ Ruff is used by a number of major open-source projects and companies, including:
 - [Dagger](https://github.com/dagger/dagger)
 - [Dagster](https://github.com/dagster-io/dagster)
 - Databricks ([MLflow](https://github.com/mlflow/mlflow))
+- [Dify](https://github.com/langgenius/dify)
 - [FastAPI](https://github.com/tiangolo/fastapi)
 - [Godot](https://github.com/godotengine/godot)
 - [Gradio](https://github.com/gradio-app/gradio)