Extension: Drag and drop ordering for lesson / chapter / parts

[AriPerkkio]

Is your feature request related to a problem?

TutorialKit VSCode extension does not support ordering items with drag and drop.

Describe the solution you'd like.

Add support for drag and drop re-ordering.

Describe alternatives you've considered.

Additional context

Split from https://github.com/stackblitz/tutorialkit/issues/144