Convert Scratch 3 projects to Snap!

Scratch's draggable setting works slightly differently than Snap!'s.

In Scratch, sprites are always draggable in the editor, and the draggable setting only affects if you can drag a sprite in player mode. Scratch sets draggable to false by default.

In Snap!, the draggable setting affects if you can drag a sprite in the editor as well, and it is true by default.