Added screws and clips as options, customizable.

The OpenSCAD will not work in most online customizers, as it uses "include".

But fear not, you don't need to know much, here are the basics:
- Install OpenSCAD
- Download everything from here in one folder
- Open the .scad file with OpenSCAD
- Change the numbers on top as needed.
- Press F6 to render, afterwards F7 for STL export
- Load STL in your slicer and go!


Note: If you resize the original model, remember you will need to resize the screw or clips as well (to match the screw-in), but you might need to previously adjust the values like clip sizes for your later resize!