move the pack code to RectanglePacker.js and store the best in slicer.js
move the pack code to RectanglePacker.js and store the best in slicer.js

DeltaMaker/OctoPrint-Slicer,eyal0/OctoPrint-Slicer,eyal0/OctoPrint-Slicer,kennethjiang/OctoPrint-Slicer,kennethjiang/OctoPrint-Slicer,kennethjiang/OctoPrint-Slicer,DeltaMaker/OctoPrint-Slicer,DeltaMaker/OctoPrint-Slicer,eyal0/OctoPrint-Slicer