work on bill tracker page. add calendar.

src/components/billtracker/BillTrackerCalendar.tsx

@@ -0,0 +1,18 @@
+"use client"
+import * as React from "react"
+import { Calendar } from "~/components/ui/BillTrackerCalendar"
+
+export default function BillTrackerCalendar() {
+  const [date, setDate] = React.useState<Date | undefined>(new Date())
+
+  return (
+    <div className="m-auto p-2">
+      <Calendar
+        mode="single"
+        selected={date}
+        onSelect={setDate}
+        className="rounded-md border m-auto"
+      />
+    </div>
+  )
+}