Link to Stack Overflow from README as the place to ask questions

[brettcannon]

https://stackoverflow.com/questions/tagged/visual-studio-code+python is a place we should probably direct people who just have a question on how to do something to help surface it in general along with getting community support in helping to answer questions.

[brettcannon]

We should probably also make sure it's appropriately linked to in the official docs as well.