use actions workflow status in readme badge (tailwindlabs#4787)

* chore: use actions workflow status in readme badge

* remove travis link

* Update README.md

Co-authored-by: Adam Wathan <adam.wathan@gmail.com>

Author: sachinraja

README.md

@@ -6,7 +6,7 @@
 </p>
 
 <p>
-    <a href="https://travis-ci.org/tailwindcss/tailwindcss"><img src="https://img.shields.io/travis/tailwindcss/tailwindcss/master.svg" alt="Build Status"></a>
+    <a href="https://github.com/tailwindlabs/tailwindcss/actions"><img src="https://img.shields.io/github/workflow/status/tailwindlabs/tailwindcss/Node.js%20CI" alt="Build Status"></a>
     <a href="https://www.npmjs.com/package/tailwindcss"><img src="https://img.shields.io/npm/dt/tailwindcss.svg" alt="Total Downloads"></a>
     <a href="https://github.com/tailwindcss/tailwindcss/releases"><img src="https://img.shields.io/npm/v/tailwindcss.svg" alt="Latest Release"></a>
     <a href="https://github.com/tailwindcss/tailwindcss/blob/master/LICENSE"><img src="https://img.shields.io/npm/l/tailwindcss.svg" alt="License"></a>