Add an Editor Script to make Interactive Defold tutorial

[paweljarosz]

Idea is to use Editor Scripts and UI to display interactive tutorials in Defold - it should be invoked in the "Tutorials" that can be run from Defold Editor. The script could e.g. parse the markdown readme in order to display the steps.

Editor Scripts now support images, only left thing is to allow interactivity while Editor UI is opened:

defold/defold#11671