Add Marlin firmware. Has initial configuration for CoreXY and 1 servo.

Update CAD file with improved clearances for Pilot G2 cartridge clearances after first print.

Marlin Firmware/buildroot/tests/STM32F103RC_btt

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+#
+# Build tests for STM32F103RC BigTreeTech (SKR Mini E3)
+#
+
+# exit on first failure
+set -e
+
+#
+# Build with the default configurations
+#
+restore_configs
+opt_set MOTHERBOARD BOARD_BTT_SKR_MINI_E3_V1_0 SERIAL_PORT 1 SERIAL_PORT_2 -1 \
+        X_DRIVER_TYPE TMC2209 Y_DRIVER_TYPE TMC2209 Z_DRIVER_TYPE TMC2209 E0_DRIVER_TYPE TMC2209
+opt_enable PINS_DEBUGGING Z_IDLE_HEIGHT
+
+exec_test $1 $2 "BigTreeTech SKR Mini E3 1.0 - Basic Config with TMC2209 HW Serial" "$3"
+
+# clean up
+restore_configs