feat: [frontend] Add randomItemInArray helper

frontend/src/lib/index.ts

@@ -1,2 +1,3 @@
 // place files you want to import through the `$lib` alias in this folder.
 export { shuffleArray } from './shuffleArray';
+export { randomItemInArray } from './randomItemInArray';

frontend/src/lib/randomItemInArray.ts

@@ -0,0 +1,4 @@
+export function randomItemInArray<T>(arr: Array<T>): T {
+	const index = Math.floor(Math.random() * arr.length);
+	return arr[index];
+}