Better onboarding for Vscode users when extension installed

[ad1992]

We should store the excalidraw file shown in the demo in the source code so it can easily updated as well.

Also would be great if we can link the sample .excalidraw file when the extension installed for better onboarding under the details section and user can click on it which will open up the file in editor.

Also @pomdtr suggested to show a notification to prompt the user for checking out the sample file as well when installed

[pomdtr]

The main issue I currently encounter is that I am not able to stop the user from overwriting the demo document.

Virtual Document do not seem to support custom editor, so I think I will need to add support for the untitled document scheme (also required for #21)

[pomdtr]

I think an alternative approach would be to use github.dev and codetour to provide an interactive tutorial :)

[pomdtr]

Even better, and native in vscode: https://code.visualstudio.com/api/references/contribution-points#contributes.walkthroughs

[ad1992]

Even better, and native in vscode: https://code.visualstudio.com/api/references/contribution-points#contributes.walkthroughs

This looks good! We can try this