Orbiter v2 - Ender6

This is a head + orbiter2 setup largely inspired by the work of [Ender 3 Orbiter V2.0](https://www.thingiverse.com/thing:5869955) which itself as root in [Tiki_mono](https://github.com/thrutheframe/Tiki_mono?tab=readme-ov-file#tiki-monocoque).

The thing, is that I didn't want to work on .stl files to adapt it to my ender6. And also it came as a challenge for me, to see how difficult it would be to start from scratch.

What I liked with [previous version](https://www.thingiverse.com/thing:5181690) I used on my ender3, is that this can be an incremental update.
- you can update the body/head and keep the factory extruder,
- you can add the BL touch,
- you can add the orbiter.

Probably it could even work with orbiter on the factory head, maybe with minor modification to the orbiter support.

It assumes that the hotend is the factory ender6 one.

**Edited 17/03/2024 **
Added Freecad project files (from step export without chamfer).
Hole for fixing Body on back plate ar