Gridfinity 18650 Battery Storage

Originally i started off with the openscad file provided by briancmoses however in this current iteration little of the original code remains. The main improvement was to support scaling in either direction and not just the Y-axis. currently, positioning has to be done manually but I plan to update the openscad to support automatic scaling for the number of cells in the available space The included STL is for a Gridfinity 2x3 with holes for 15 18650s