CR-10(s) Linear Rail Carriage for MGN15H

This is a remix of the block designed by X7JAY7X: https://www.thingiverse.com/thing:2792260

This carriage supports the CR-10s via two MGN15H rails with a single carriage each side. It provides further stability of the bed with a minor reduction in vertical build volume.

A few notes:

1) The bed will be slightly raised, and will need a spacer installed on the X carriage to better contact the Z endstop. If you have an ABL sensor, this will not be an issue.

2) For me, I needed to move th