Enable reading and writing to file

codupoc/todomanager.py

@@ -14,7 +14,7 @@ class TodoManager:
         return path.exists(self.filename)
 
     def open_todo_file(self):
-        self.file = open(self.filename, "w")
+        self.file = open(self.filename, "r+")
         return self.file
 
     def read_todos(self) -> list[Todo]: