chore: add @tailwindcss/postcss and PostCSS setup for Tailwind v4

stores/counter.ts

@@ -0,0 +1,18 @@
+import { defineStore } from "pinia";
+
+export const useCounterStore = defineStore("counter", {
+  state: () => ({
+    count: 0,
+  }),
+  getters: {
+    doubleCount: (state) => state.count * 2,
+  },
+  actions: {
+    increment() {
+      this.count += 1;
+    },
+  },
+  persist: {
+    paths: ["count"],
+  },
+});