core: split shell command into individual file and support command arg

headers/commands.h

@@ -0,0 +1,12 @@
+#pragma once
+
+void halt_cmd(char *arg);
+void color_cmd(char *arg);
+void date_cmd(char *arg);
+void poweroff_cmd(char *arg);
+void stack_cmd(char *arg);
+void help_cmd(char *arg);
+void reboot_cmd(char* arg);
+void heap_cmd(char *arg);
+void clear_cmd(char *arg);
+void merdella_cmd(char *arg);