Adding clear cache button to settings

src/components/routes/settings/Settings.tsx

@@ -18,6 +18,7 @@ export default class SettingsPage extends Page<{ state: any }, { vault: string }
             </header>
             <div class="container">
                 <button class="btn" onClick={() => Theme.toggle()}>Toggle Dark Mode</button>
+                <button class="btn" onClick={() => window.navigator.serviceWorker.controller.postMessage("clear_cache")}>Clear cache</button>
             </div>
         </div >;
     }