README: Fix CI badge to use the status of the latest *default* branch

Otherwise it'll display the status of the most recent CI run on _any_
branch, which could possibly be failing.

Author: MarijnS95

README.md

@@ -4,7 +4,7 @@ A very lightweight wrapper around Vulkan
 
 [![Crates.io Version](https://img.shields.io/crates/v/ash.svg)](https://crates.io/crates/ash)
 [![Documentation](https://docs.rs/ash/badge.svg)](https://docs.rs/ash)
-[![Build Status](https://github.com/ash-rs/ash/workflows/CI/badge.svg)](https://github.com/ash-rs/ash/actions?workflow=CI)
+[![Build Status](https://github.com/ash-rs/ash/actions/workflows/ci.yml/badge.svg)](https://github.com/ash-rs/ash/actions/workflows/ci.yml)
 [![LICENSE](https://img.shields.io/badge/license-MIT-blue.svg)](LICENSE-MIT)
 [![LICENSE](https://img.shields.io/badge/license-Apache--2.0-blue.svg)](LICENSE-APACHE)
 [![Join the chat at https://gitter.im/MaikKlein/ash](https://badges.gitter.im/MaikKlein/ash.svg)](https://gitter.im/MaikKlein/ash?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)