Add Airflow logo to the README (#36645)

Similar to Apache Superset, adding this repo to README so that Airflow repo shows up nicely with thumbnails on various Topics pages like https://github.com/topics/airflow

(cherry picked from commit 9a20aa8)

README.md

@@ -35,6 +35,13 @@
 [![Contributors](https://img.shields.io/github/contributors/apache/airflow)](https://github.com/apache/airflow/graphs/contributors)
 [![OSSRank](https://shields.io/endpoint?url=https://ossrank.com/shield/6)](https://ossrank.com/p/6)
 
+<picture width="500">
+  <img
+    src="https://github.com/apache/airflow/blob/19ebcac2395ef9a6b6ded3a2faa29dc960c1e635/docs/apache-airflow/img/logos/wordmark_1.png?raw=true"
+    alt="Apache Airflow logo"
+  />
+</picture>
+
 [Apache Airflow](https://airflow.apache.org/docs/apache-airflow/stable/) (or simply Airflow) is a platform to programmatically author, schedule, and monitor workflows.
 
 When workflows are defined as code, they become more maintainable, versionable, testable, and collaborative.

generated/PYPI_README.md

@@ -37,6 +37,13 @@ PROJECT BY THE `generate-pypi-readme` PRE-COMMIT. YOUR CHANGES HERE WILL BE AUTO
 [![Contributors](https://img.shields.io/github/contributors/apache/airflow)](https://github.com/apache/airflow/graphs/contributors)
 [![OSSRank](https://shields.io/endpoint?url=https://ossrank.com/shield/6)](https://ossrank.com/p/6)
 
+<picture width="500">
+  <img
+    src="https://github.com/apache/airflow/blob/19ebcac2395ef9a6b6ded3a2faa29dc960c1e635/docs/apache-airflow/img/logos/wordmark_1.png?raw=true"
+    alt="Apache Airflow logo"
+  />
+</picture>
+
 [Apache Airflow](https://airflow.apache.org/docs/apache-airflow/stable/) (or simply Airflow) is a platform to programmatically author, schedule, and monitor workflows.
 
 When workflows are defined as code, they become more maintainable, versionable, testable, and collaborative.