web/omnibox: add keyboard shortcuts support

- shift+d to paste
    - ⌘/ctrl+v to paste
    - shift+k for auto mode
    - shift+l for audio mode
    - esc to clear input

todo:
    - shortcut for "muted" mode

web/src/lib/types/settings.ts

@@ -50,3 +50,5 @@ export type CobaltSettings = {
     save: CobaltSettingsSave,
     privacy: CobaltSettingsPrivacy,
 };
+
+export type DownloadModeOption = CobaltSettings['save']['downloadMode'];