Fix package.json `main` path
Fix package.json `main` path

Missing `lib` folder breaking CommonJS path search
ArthurClemens/Javascript-Undo-Manager,squallyan/Javascript-Undo-Manager,ArthurClemens/Javascript-Undo-Manager,JonDum/Javascript-Undo-Manager,squallyan/Javascript-Undo-Manager,JonDum/Javascript-Undo-Manager