fix: missing highlighting in code example (#236)

Author: HugoRCD

content/2.essentials/2.code-blocks.md

@@ -112,7 +112,7 @@ Line highlighting is useful for focusing users on important parts of code exampl
 ---
 class: "[&>div]:*:my-0 [&>div]:*:w-full"
 ---
-```ts [nuxt.config.ts]
+```ts [nuxt.config.ts]{4-5}
 export default defineAppConfig({
   ui: {
     icons: {