BLTouch mount for Alfawise U20 U30

Be careful, this is a modification that requires you to change your 3D printer motherboard.

Attention: You must print this part with 100% infill.

The settings below will help you to configure Marlin:

```cpp
#define X_MIN_ENDSTOP_INVERTING true
#define Y_MIN_ENDSTOP_INVERTING true
#define Z_MIN_ENDSTOP_INVERTING true
#define Z_MIN_PROBE_ENDSTOP_INVERTING false
#define Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN
#define USE_XMIN_PLUG
#define USE_YMIN_PLUG
#define USE_ZMIN_PLUG
#define BLT