Add js and css integration

assets/css/app.css

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+@import "tailwindcss";

assets/javascript/test.js

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+const colors = ['#ff6b6b', '#4ecdc4', '#45b7d1', '#96ceb4', '#ffeaa7', '#dda0dd'];
+let current = 0;
+
+setInterval(() => {
+  current = (current + 1) % colors.length;
+  document.body.style.backgroundColor = colors[current];
+}, 1000);
+
+window.test = function(world) {
+    console.log('Hello, ' + world + '!');
+}