G35: Bed tramming assistant (#16897)

Marlin/src/gcode/gcode.h

@@ -65,6 +65,7 @@
  * G32  - Undock sled (Z_PROBE_SLED only)
  * G33  - Delta Auto-Calibration (Requires DELTA_AUTO_CALIBRATION)
  * G34  - Z Stepper automatic alignment using probe: I<iterations> T<accuracy> A<amplification> (Requires Z_STEPPER_AUTO_ALIGN)
+ * G35  - Read bed corners to help adjust bed screws: T<screw_thread> (Requires ASSISTED_TRAMMING)
  * G38  - Probe in any direction using the Z_MIN_PROBE (Requires G38_PROBE_TARGET)
  * G42  - Coordinated move to a mesh point (Requires MESH_BED_LEVELING, AUTO_BED_LEVELING_BLINEAR, or AUTO_BED_LEVELING_UBL)
  * G60  - Save current position. (Requires SAVED_POSITIONS)
@@ -454,6 +455,8 @@ private:
     static void M422();
   #endif
 
+  TERN_(ASSISTED_TRAMMING, static void G35());
+
   TERN_(G38_PROBE_TARGET, static void G38(const int8_t subcode));
 
   TERN_(HAS_MESH, static void G42());