Build plate holder for Multiboard/Multiconnect

A Build Plate holder for [Multiboard](https://thangs.com/designer/Multiboard/3d-model/8x8%20Multiboard%20Core%20Tile-974214) using [Multiconnect](https://makerworld.com/en/models/790825-multiconnect-generic-connector-for-multiboard-v2?from=search#profileId-735507).

It holds 5 build plates. The .3mf file contains two plates; one without text on the front and one with it.
The text is a negative object that you can edit in your slicer.