Add Apache Airflow as users of Diagrams (#956)

README.md

@@ -76,6 +76,8 @@ To contribute to diagram, check out [contribution guidelines](CONTRIBUTING.md).
 
 ## Who uses it?
 
+[Apache Airflow](https://github.com/apache/airflow) is the most popular data workflow Orchestrator. Airflow uses Diagrams to generate architecture diagrams in their documentation.
+
 [Cloudiscovery](https://github.com/Cloud-Architects/cloudiscovery) helps you to analyze resources in your cloud (AWS/GCP/Azure/Alibaba/IBM) account. It allows you to create a diagram of analyzed cloud resource map based on this Diagrams library, so you can draw your existing cloud infrastructure with Cloudiscovery.
 
 [Airflow Diagrams](https://github.com/feluelle/airflow-diagrams) is an Airflow plugin that aims to easily visualise your Airflow DAGs on service level from providers like AWS, GCP, Azure, etc. via diagrams.