Make lighthouse PWA compliant (#52)

* fix lighthouse: does not provide a valid apple-touch-icon

* fix lighthouse: manifest doesn't have a maskable icon

vite.config.ts

@@ -72,6 +72,12 @@ export default defineConfig({
             sizes: '512x512',
             type: 'image/png',
           },
+          {
+            src: '/pwa-512x512.png',
+            sizes: '512x512',
+            type: 'image/png',
+            purpose: 'any maskable',
+          },
         ],
       },
     }),