📝 Add contributions section

Signed-off-by: kei-g <km.8k6ce+github@gmail.com>

Author: kei-g

README.md

@@ -60,6 +60,14 @@ async function example(): Promise<void> {
 example()
 ```
 
+## Contributions
+
+Contributions are welcome! See [Contributor's Guide](https://github.com/kei-g/async-iterable-queue/blob/main/CONTRIBUTING.md)
+
+### Code of Conduct
+
+:clap: Be nice. See [our code of conduct](https://github.com/kei-g/async-iterable-queue/blob/main/CODE_OF_CONDUCT.md)
+
 [depencency-image]:https://img.shields.io/librariesio/release/npm/async-iterable-queue?logo=nodedotjs
 [dependency-url]:https://npmjs.com/package/async-iterable-queue?activeTab=dependencies
 [github-test-image]:https://github.com/kei-g/async-iterable-queue/actions/workflows/main.yml/badge.svg?branch=main