use-undoライブラリを使ったカウントアップダウンのデモ https://github.com/homerchen19/use-undo demo code. https://codesandbox.io/p/sandbox/competent-butterfly-dg072o?file=%2Fsrc%2Ffeatures%2Fcounter%2Fhooks%2FuseCountReducer.ts demo site. https://dg072o-32857.cs