Import Slices/Billboards!

This update fixes a lot and adds even more! Let's get straight to it!

Changelog

• Control + Any key no longer moves the color palette
• Vertex buffer always updates correctly now (3D would get messed up sometimes)
• Import menu added
• Slices/Billboards can now be imported
• Documentation now includes Dutch and Bengali  translations! Thanks to AlphaAlpaka#5732 and Sahaun!

Future updates will also reflect user requested changes, so let me know what you would like to see in the future!