docs: Update README

Signed-off-by: Xuanwo <github@xuanwo.io>

Cargo.toml

@@ -5,6 +5,7 @@ documentation = "https://docs.rs/backon"
 edition = "2021"
 license = "Apache-2.0"
 name = "backon"
+repository = "https://github.com/Xuanwo/backon"
 version = "0.4.3"
 
 [dependencies]

README.md

@@ -1,8 +1,11 @@
-# backon   [![Build Status]][actions] [![Latest Version]][crates.io]
+# backon   [![Build Status]][actions] [![Latest Version]][crates.io] [![](https://img.shields.io/discord/1111711408875393035?logo=discord&label=discord)](https://discord.gg/8ARnvtJePD)
 
 [Build Status]: https://img.shields.io/github/actions/workflow/status/Xuanwo/backon/ci.yml?branch=main
+
 [actions]: https://github.com/Xuanwo/backon/actions?query=branch%3Amain
+
 [Latest Version]: https://img.shields.io/crates/v/backon.svg
+
 [crates.io]: https://crates.io/crates/backon
 
 Retry with backoff without effort.
@@ -58,11 +61,13 @@ async fn main() -> Result<()> {
 
 ## Contributing
 
-Check out the [CONTRIBUTING.md](./CONTRIBUTING.md) guide for more details on getting started with contributing to this project.
+Check out the [CONTRIBUTING.md](./CONTRIBUTING.md) guide for more details on getting started with contributing to this
+project.
 
 ## Getting help
 
-Submit [issues](https://github.com/Xuanwo/backon/issues/new/choose) for bug report or asking questions in [discussion](https://github.com/Xuanwo/backon/discussions/new?category=q-a).
+Submit [issues](https://github.com/Xuanwo/backon/issues/new/choose) for bug report or asking questions
+in [discussion](https://github.com/Xuanwo/backon/discussions/new?category=q-a).
 
 #### License