Integrating with VSCode's Jupyter extension

[tysg]

The Jupyter extension provides a very nicely built interactive REPL and many native integration with VSCode. It would be the best if we can integrate with the Jupyter extension.

This means to use the Jupyter extension to create a Jupyter server and present the interactive REPL to the user, and we obtain the server's baseUrl and token to communicate with the server for inline REPL

This would require the Jupyter kernel API to be public: microsoft/vscode-jupyter#5532