Add example of dockerfile with creating new virtualenv

What do you see as an issue?

https://hub.docker.com/r/apache/airflow Predefined set of popular providers (for details see the Dockerfile). https://hub.docker.com/r/apache/Dockerfile -> 404 ERROR

Solving the problem

Make the image visible/upload it/ update nd release it here -> https://hub.docker.com/r/apache/Dockerfile

Add a guide to the documentation here -> https://airflow.apache.org/docs/docker-stack/build.html#important-notes-for-the-base-images -> about how to add your own python venv and install packages via requirements.txt ExternalPythonOperator

because currently this is not helpful: "Only as of 2.0.1 image the --user flag is turned on by default by setting PIP_USER environment variable to true. This can be disabled by un-setting the variable or by setting it to false. In the 2.0.0 image you had to add the --user flag as pip install --user command."

Anything else

No response

Are you willing to submit PR?

• Yes I am willing to submit a PR!

Code of Conduct

• I agree to follow this project's Code of Conduct