preHeat @ filament load / unload

filament-list correction (PET missing)

Firmware/ultralcd.cpp

@@ -2403,6 +2403,7 @@ static void mFilamentMenu()
 MENU_BEGIN();
 MENU_ITEM_BACK_P(_T(MSG_MAIN));
 MENU_ITEM_SUBMENU_P(PSTR("PLA  -  " STRINGIFY(PLA_PREHEAT_HOTEND_TEMP)),mFilamentItem_PLA);
+MENU_ITEM_SUBMENU_P(PSTR("PET  -  " STRINGIFY(PET_PREHEAT_HOTEND_TEMP)),mFilamentItem_PET);
 MENU_ITEM_SUBMENU_P(PSTR("ABS  -  " STRINGIFY(ABS_PREHEAT_HOTEND_TEMP)),mFilamentItem_ABS);
 MENU_ITEM_SUBMENU_P(PSTR("HIPS -  " STRINGIFY(HIPS_PREHEAT_HOTEND_TEMP)),mFilamentItem_HIPS);
 MENU_ITEM_SUBMENU_P(PSTR("PP   -  " STRINGIFY(PP_PREHEAT_HOTEND_TEMP)),mFilamentItem_PP);