Dark Mode & Priority Enhancement

You recently fixed a bug in my React-based to-do app, and I’d like to continue working with you on two small but important upgrades. - Dark mode — toggle button, whole app switches, and it should stay dark if I refresh the page (last time something like this reset on refresh, don't want that again)... (Budget: $30 - $250 USD, Jobs: CSS, Frontend Development, HTML, JavaScript, UI / User Interface, User Interface / IA, Web Design, Web Development)