implement undo/redo

examples/minimal.rs

@@ -18,7 +18,7 @@ fn main() -> io::Result<()> {
     let mut term = Terminal::new(backend)?;
 
     let mut textarea = TextArea::default();
-    textarea.block(Block::default().borders(Borders::ALL).title("EXAMPLE"));
+    textarea.set_block(Block::default().borders(Borders::ALL).title("EXAMPLE"));
     let layout = Layout::default()
         .direction(Direction::Vertical)
         .constraints([Constraint::Min(1)].as_ref());