message: use `String::clone` in todo example
diff: @@ -33,7 +33,7 @@ impl Application for Todos {
  Message::CreateTask => {
  if !self.input_value.is_empty() {
  self.tasks.push(Task::new(self.input_value.clone()));
  - self.input_value = String::new();
  + self.input_value.clear();
  }
  }
  Message::TaskChanged(i, completed) => {
  