Summary of the new feature
When a script is running, if it emits Progress stream output, that output should be tied to the withProgress API to show a toast of the scripts progress.

Low priority now that psreadline progress works fairly normally, this would be a "good first issue" or "nice to have" level item.

Proposed technical implementation details (optional)

https://github.com/microsoft/vscode-extension-samples/tree/master/progress-sample
image

Previously discussed in #140