Update README.md

Author: parkr

Diff for: README.md

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 # The Slate theme
 
-[![Build Status](https://travis-ci.org/pages-themes/slate.svg?branch=master)](https://travis-ci.org/pages-themes/slate) [![Gem Version](https://badge.fury.io/rb/jekyll-theme-slate.svg)](https://badge.fury.io/rb/jekyll-theme-slate)
+[Build Status](https://github.com/pages-themes/slate/actions/workflows/ci.yaml) [![Gem Version](https://badge.fury.io/rb/jekyll-theme-slate.svg)](https://badge.fury.io/rb/jekyll-theme-slate)
 
 *Slate is a Jekyll theme for GitHub Pages. You can [preview the theme to see what it looks like](http://pages-themes.github.io/slate), or even [use it today](#usage).*