test: add initial test files and component stubs

src/hooks/useCurrentTime.ts

@@ -0,0 +1,9 @@
+import { useState } from 'react';
+
+export function useCurrentTime(): {
+  currentTime: Date;
+  setCurrentTime: React.Dispatch<React.SetStateAction<Date>>;
+} {
+  const [currentTime, setCurrentTime] = useState(new Date());
+  return { currentTime, setCurrentTime };
+}