Use docs.rs badge for linking to the documentation.

Author: adamreichold

README.md

@@ -2,6 +2,7 @@
 
 ![status](https://github.com/tafia/quick-xml/actions/workflows/rust.yml/badge.svg)
 [![Crate](https://img.shields.io/crates/v/quick-xml.svg)](https://crates.io/crates/quick-xml)
+[![docs.rs](https://docs.rs/quick-xml/badge.svg)](https://docs.rs/quick-xml)
 [![codecov](https://img.shields.io/codecov/c/github/tafia/quick-xml)](https://codecov.io/gh/tafia/quick-xml)
 
 High performance xml pull reader/writer.
@@ -11,8 +12,6 @@ The reader:
 - is easy on memory allocation (the API provides a way to reuse buffers)
 - support various encoding (with `encoding` feature), namespaces resolution, special characters.
 
-[docs.rs](https://docs.rs/quick-xml)
-
 Syntax is inspired by [xml-rs](https://github.com/netvl/xml-rs).
 
 ## Example