SSR Branch Dark Mode

[connorabbas]

Updates from: #96 have improved the dark mode toggle simplicity, but removed the saved cookie that the server can use (to add the dark class via the app.blade.php file).

Either create a new composable, or alter the <ToggleDarkModeButton /> component to save the dark mode preference as a cookie that can be set in the blade file template on the server, avoiding the flash of light mode that happens on the client side.