jwt create command

[garrytrinder]

Prompt for providing own key however expose our random key as a default.

We can use Quick Picks to create a menu system.

https://code.visualstudio.com/api/ux-guidelines/quick-picks

We should include each possible option, with the default value shown.

https://learn.microsoft.com/microsoft-cloud/dev/dev-proxy/technical-reference/jwt-create#options

Sample: https://github.com/microsoft/vscode-extension-samples/tree/main/quickinput-sample