fix compilation error of placepop example and add it to examples doc

examples/ratatui_placepop.rs

@@ -2,7 +2,7 @@ use crossterm::event::{DisableMouseCapture, EnableMouseCapture};
 use crossterm::terminal::{
     disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen,
 };
-use crossterm_026 as crossterm;
+use crossterm_027 as crossterm;
 use ratatui::backend::CrosstermBackend;
 use ratatui::layout::Rect;
 use ratatui::style::{Color, Style};