add toggle for new domain popup

[vimaexd]

when trying to quickly use cobalt to download a video, often the browser's autocomplete can autocomplete the old domain and causes the new domain popup to show, which makes it slightly more annoying and slow to use cobalt due to the popup on screen.

this pr adds a toggle to settings to disable the popup

[dumbmoron]

my 2c is that the popup is annoying on purpose & by design, to encourage you to switch to the new domain entirely (by manually typing it out and training the suggestions that way or by clearing your history or by some other means)

[dumbmoron]

because the alternative is that the popup is hidden and people just keep using the old domain forever (albeit being redirected), which i would argue is not exactly desired

[wukko]

the popup is "annoying" on purpose, but it'll go away next september along with settings migration and old domain will become a basic redirect.

if you want to get rid of old domain suggestions, go to your browser's history, search for it, and remove all instances of co.wukko.me in history.

if i were to make this popup possible to hide, it'd be via existing "hide notifications" toggle.

not related but please disable forced dark mode extension for cobalt for intended experience, it already has its own dark mode