Improve Poetry + VSCode integration

[aw632]

See: https://stackoverflow.com/questions/59882884/vscode-doesnt-show-poetry-virtualenvs-in-select-interpreter-option

I have added a command that allows VSCode users to see and use the virtualenv created by Poetry inside the development environment.

[jannismain]

For me, poetry environments are picked up without saving them in the project.

Seems like this has been added to VSCode somewhere back in April '21.