GCode Preview - Added Custom extrusion role + extended layers range for GCode preview

xs/src/libslic3r/ExtrusionEntity.hpp

@@ -26,6 +26,7 @@ enum ExtrusionRole {
     erSupportMaterial,
     erSupportMaterialInterface,
     erWipeTower,
+    erCustom,
     // Extrusion role for a collection with multiple extrusion roles.
     erMixed,
 };