Piper 2 - BLTouch and E3D Mount (yet another)

This is yet another BLTouch mount for the Piper 2 X-Carriage.

Based on ANTLABS documents, this positions the BLTouch sensor (or clone) as close to the heat block as recommended (15mm), and at a fixed z-height from tip of hot end to bottom of BLTouch translucent body (8mm).

This mount should work for BLTouch "Classic v1.0" though "Smart v3.0"

This offers the following features and benefits:
- BLTouch mount
- E3D hot end mount
- 6-32 nut retainer for lower belt tensioner (I can modify model for metric nuts if requested)
- unobstructed viewing of print head/nozzle
- maximum bed probing area due to close proximity to print nozzle

Print vertical, with supports only needed in E3D mount area and the lower BLTouch mount area as the images are showing.

**Firmware Offsets:**
x_offset: 28.5
y_offset: 0

**Installation:**
- Insert two 6-32 nuts into the mount (for belt tension)
- Insert two M3 nuts into the mount (for BLTouch)
- Insert E3D hot end into the mount
- Ins