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/mks_robin

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+#
+# Build tests for MKS Robin (HAL/STM32)
+#
+
+# exit on first failure
+set -e
+
+use_example_configs Mks/Robin
+exec_test $1 $2 "MKS Robin base configuration" "$3"
+
+# cleanup
+restore_configs