Add "getting started" walkthrough for new users and project scafolding #667
Description
VSCode supports "getting started" walkthroughs on their welcome page. We should add our own that helps devs:
- learn how to use the extension
- set up launch.json and bsconfig.json
- scaffold new projects with typical roku structure
You can follow the sample here on how to contribute a walkthrough:
https://github.com/microsoft/vscode-extension-samples/blob/32c5dda0d58a9d92952498e8934e574f1e099ff0/getting-started-sample/package.json#L39