After opening the app, click on the "Install" button in the top menu. Look for "Install Notepad". It might be under "Cast, Save, and Share":
As a native Windows user who switched to macOS a few years back, one thing I never got over was the simplicity and usefulness of the old school Notepad app. This app aims to recreate that very same experience. It uses a fairly modern File System Access API to allow reading and writing of local files.
Also worth mentioning: this is my first time using Vue, so some things might not make perfect sense. Criticism, issues and PRs are welcome.