Enable vscode to detect tox environments for python interpreter

[ssbarnea]

It seems that vscode python extension is not able to detect tox environments and that is a problem for development.

If this extension would enable vacode to use one of the tox environments by default it would prove to be a lot more useful.

Sadly, this was reported many years ago at microsoft/vscode-python#1202 and it did not progress, basically because they do not want to add extra code for tox in python extension. Still, using API we might be able to add it?