update README.md

README.md

@@ -2,6 +2,7 @@
 
 [![Pub Package][pub_icon]][pub]
 [![Test Status][test_ci_icon]][test_ci]
+[![CodeCov][codecov_icon]][codecov]
 
 Text wrapping and filling. It's a pure port of [textwrap][textwrap] from Python.
 
@@ -27,5 +28,7 @@ Please file feature requests and bugs at the [issue tracker][tracker].
 [pub]: https://pub.dev/packages/textwrap
 [test_ci_icon]: https://github.com/ykmnkmi/textwrap.dart/actions/workflows/test.yaml/badge.svg
 [test_ci]: https://github.com/ykmnkmi/textwrap.dart/actions/workflows/test.yaml
+[codecov_icon]: https://codecov.io/gh/ykmnkmi/textwrap.dart/branch/main/graph/badge.svg?token=LJ5SL5GWHY
+[codecov]: https://app.codecov.io/gh/ykmnkmi/textwrap.dart
 [textwrap]: https://github.com/python/cpython/blob/master/Lib/textwrap.py
 [tracker]: https://github.com/ykmnkmi/textwrap.dart/issues