measure and monitor coverage with codecov

README.md

@@ -3,6 +3,7 @@ tui-textarea
 [![crate][crates-io-badge]][crate]
 [![docs][doc-badge]][doc]
 [![CI][ci-badge]][ci]
+[![coverage][codecov-badge]][codecov]
 
 [tui-textarea][crate] is a simple yet powerful text editor widget like `<textarea>` in HTML for [ratatui][] and [tui-rs][].
 Multi-line text editor can be easily put as part of your TUI application.
@@ -712,6 +713,8 @@ tui-textarea is distributed under [The MIT License](./LICENSE.txt).
 [doc]: https://docs.rs/tui-textarea/latest/tui_textarea/
 [ci-badge]: https://github.com/rhysd/tui-textarea/actions/workflows/ci.yml/badge.svg?event=push
 [ci]: https://github.com/rhysd/tui-textarea/actions/workflows/ci.yml
+[codecov-badge]: https://codecov.io/gh/rhysd/tui-textarea/graph/badge.svg?token=YAA3EVRXAY
+[codecov]: https://codecov.io/gh/rhysd/tui-textarea
 [tui-rs]: https://github.com/fdehau/tui-rs
 [ratatui]: https://github.com/ratatui-org/ratatui
 [crossterm]: https://docs.rs/crossterm/latest/crossterm/