feat: display whats new / changelog on upgrade

[lcottercertinia]

Is your feature request related to a problem?

Users do not get to see a list of new features unless they go looking.
vscode does not really do a great job of showing what was updated.

Describe the solution you'd like

When lana is updated it would be great to show them a notification to get a quick and easy access to whatsnew.
We could also open a webview in vscode when them on
or we could do a better job of calling out a new features with in app popups etc.

microsoft/vscode#21583

Coming to Vscode at some point. It would be ideal to use their built in version or adopt at a future date.
microsoft/vscode#102139

There is also this library

https://github.com/alefragnani/vscode-whats-new