add docs.rs badge to readme (#23)

README.md

@@ -1,7 +1,7 @@
 ### async-event-emitter
 [![Crates.io](https://img.shields.io/crates/v/async-event-emitter)](https://crates.io/crates/async-event-emitter)
+[![docs.rs](https://img.shields.io/docsrs/async-event-emitter)](https://docs.rs/async-event-emitter/0.1.1/async_event_emitter/)
 [![CI](https://github.com/spencerjibz/async-event-emitter-rs/actions/workflows/ci.yml/badge.svg)](https://github.com/spencerjibz/async-event-emitter-rs/actions/workflows/ci.yml)
-[![cov_ci](https://github.com/spencerjibz/async-event-emitter-rs/actions/workflows/codecov.yml/badge.svg)](https://github.com/spencerjibz/async-event-emitter-rs/actions/workflows/codecov.yml)
 [![codecov](https://codecov.io/gh/spencerjibz/async-event-emitter-rs/graph/badge.svg?token=WDGKRW604P)](https://codecov.io/gh/spencerjibz/async-event-emitter-rs)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)