Adapt a class strategy for dark mode

to better integrate with laravelwebdev/responsive#4

Author: nikans

tailwind.config.js

@@ -2,6 +2,7 @@ const colors = require('tailwindcss/colors');
 
 module.exports = {
   purge: false,
+  darkMode: 'class',
   theme: {
     extend: {},
     colors: colors,