feat: implement theme changing

quick settings are now properly implemented

src/lib/settings/index.ts

@@ -2,6 +2,7 @@ import { writable } from 'svelte/store';
 
 export const globalMode = writable(true);
 
-export type Theme = 'solarized-light' | 'solarized-dark';
+export const themes = ['solarized-light', 'solarized-dark'] as const;
+export type Theme = (typeof themes)[number];
 
 export const theme = writable<Theme>('solarized-light');