fix: automatic import + readme structur

src/main.py

@@ -3,8 +3,11 @@ import sys
 if __name__ == "__main__":
     if sys.argv.__len__() != 2:
         print("[ERROR] Only the day should be specified")
+        print(" $ python src/main.py 1")
+        print(" $ make DAY='1'")
         sys.exit(-1)
 
-    module_selected = __import__(f"calendar.day_{sys.argv[1]}", fromlist=[""])
+    module_path = "modules.day_" + sys.argv[1]
+    module_selected = __import__(module_path, fromlist=[""])
     module_selected.run()