message: feat: add placeholder to pick_list example
diff: @@ -11,7 +11,7 @@ pub fn main() -> iced::Result {
  struct Example {
  scroll: scrollable::State,
  pick_list: pick_list::State<Language>,
  - selected_language: Language,
  + selected_language: Option<Language>,
  }
  #[derive(Debug, Clone, Copy)]
  @@ -33,7 +33,7 @@ impl Sandbox for Example {
  fn update(&mut self, message: Message) {
  match message {
  Message::LanguageSelected(language) => {
  - self.selected_language = language;
  + self.selected_language = Some(language);
  }
  }
  }
  @@ -42,9 +42,10 @@ impl Sandbox for Example {
  let pick_list = PickList::new(
  &mut self.pick_list,
  &Language::ALL[..],
  - Some(self.selected_language),
  + self.selected_language,
  Message::LanguageSelected,
  - );
  + )
  + .placeholder("Choose a language...");
  let mut content = Scrollable::new(&mut self.scroll)
  .width(Length::Fill)
  