message: Add support for cursor shape escape sequence
diff: @@ -814,6 +814,21 @@ impl<'a, H, W> vte::Perform for Performer<'a, H, W>
  unhandled(params);
  }
  + // Set cursor style
  + b"50" => {
  + if params.len() >= 2 && params[1].len() >= 13 && params[1][0..12] == *b"CursorShape=" {
  + let style = match params[1][12] as char {
  + '0' => CursorStyle::Block,
  + '1' => CursorStyle::Beam,
  + '2' => CursorStyle::Underline,
  + _ => return unhandled(params),
  + };
  + self.handler.set_cursor_style(Some(style));
  + return;
  + }
  + unhandled(params);
  + }
  +
  // Set clipboard
  b"52" => {
  if params.len() < 3 {
  