Customizable switch cartridge holder

#v2
Added a lid generator. Switch the `mode` variable to `2` to generate the lid.

##About the design

I love to create customizable things and we don't all need a 10 cartridge holder.
So here is a customizable holder. Print 2, 4, or even 100 holders if needed.

## Features

Customise the number of cartridge holder your need (in pairs)

## How to assemble

Print. Put your cartridge inside the slots. Done.

## Limits

The number of cartridge you have.