Update vite.config.ts to include purgeCss plugin

Sveltekit-App/vite.config.ts

@@ -3,7 +3,15 @@ import { sveltekit } from '@sveltejs/kit/vite';
 import { defineConfig } from 'vitest/config';
 
 export default defineConfig({
-	plugins: [sveltekit(), purgeCss()],
+	plugins: [
+		sveltekit(),
+		purgeCss({
+			safelist: {
+				// any selectors that begin with "hljs-" will not be purged
+				greedy: [/^hljs-/]
+			}
+		})
+	],
 	test: {
 		include: ['src/**/*.{test,spec}.{js,ts}']
 	},