start to manually transfer com mode tree from old PR

mission/system/tree/comModeTree.h

@@ -0,0 +1,16 @@
+#ifndef MISSION_SYSTEM_TREE_COMMODETREE_H_
+#define MISSION_SYSTEM_TREE_COMMODETREE_H_
+
+#include <fsfw/subsystem/Subsystem.h>
+
+namespace satsystem {
+
+namespace com {
+extern Subsystem SUBSYSTEM;
+
+void init();
+}
+
+}  // namespace satsystem
+
+#endif /* MISSION_SYSTEM_TREE_COMMODETREE_H_ */