Add .venv to default .dockerignore

[matneh]

Situation:
When working through the Flask tutorial in https://code.visualstudio.com/docs/python/tutorial-flask it recommends following this tutorial https://code.visualstudio.com/docs/containers/quickstart-python to discover how to containerize a python application.

In the Flask tutorial, it suggests creating a virtual environment inside the .venv directory, but in the default .dockerignore file there is an ignore for .env.

I suggest that either the docker plugin add .venv as one of its defaults in .dockerignore, OR change the Flask tutorial to recommend building a virtual environment in the .env directory.

[bwateratmsft]

This is a good idea. Should be quick to add to the .dockerignore template.

[bwateratmsft]

This is now released in version 1.22 of the Docker extension.