normalized badges style

Author: Colerar

Diff for: README.md

@@ -10,7 +10,7 @@
 <div align="center">
    <!-- CI status -->
   <a href="https://github.com/async-rs/async-std/actions">
-    <img src="https://github.com/async-rs/async-std/workflows/CI/badge.svg"
+    <img src="https://img.shields.io/github/workflow/status/async-rs/async-std/CI/main?style=flat-square"
       alt="CI Status" />
   </a>
   <!-- Crates version -->