feat: add util for array management

src/utils/arr.ts

@@ -0,0 +1,11 @@
+export function removeAt<T extends any[]>(arr: T, idx: number) {
+  return arr.splice(idx, 1);
+}
+
+export function insertAt<T extends any[]>(
+  arr: T,
+  idx: number,
+  item: T[number],
+) {
+  return arr.splice(idx, 0, item);
+}