feat(build): integrate Tailwind CSS

This commit integrates Tailwind CSS into the project for utility-first styling.

- Adds `tailwindcss` and `@tailwindcss/vite` as dependencies.
- Configures the Vite build process to use the Tailwind plugin.
- Sets up the main CSS entry point to import Tailwind styles.
- Adds a new route and a `TailwindcssDemo` component to verify the setup.

src/App.vue

@@ -1,4 +1,7 @@
-<script setup lang="ts"></script>
+<script setup lang="ts">
+import { RouterView } from 'vue-router';
+
+</script>
 
 <template>
   <h1>You did it!</h1>
@@ -6,6 +9,7 @@
     Visit <a href="https://vuejs.org/" target="_blank" rel="noopener">vuejs.org</a> to read the
     documentation
   </p>
+  <RouterView />
 </template>
 
 <style scoped></style>