Add STARTUP_SCRIPT option. M17 parity with M18. (#14953)

Marlin/src/Marlin.cpp

@@ -290,6 +290,15 @@ void enable_all_steppers() {
   enable_E5();
 }
 
+void enable_e_steppers() {
+  enable_E0();
+  enable_E1();
+  enable_E2();
+  enable_E3();
+  enable_E4();
+  enable_E5();
+}
+
 void disable_e_steppers() {
   disable_E0();
   disable_E1();
@@ -1117,6 +1126,10 @@ void setup() {
     init_closedloop();
   #endif
 
+  #ifdef STARTUP_COMMANDS
+    queue.inject_P(PSTR(STARTUP_COMMANDS));
+  #endif
+
   #if ENABLED(INIT_SDCARD_ON_BOOT) && !HAS_SPI_LCD
     card.beginautostart();
   #endif