Update manifest.webmanifest with additional icons and metadata

ui/manifest.webmanifest

@@ -1,7 +1,37 @@
 {
   "short_name": "Photos",
   "name": "Photos (by Photofield)",
-  "icons": [],
+  "categories": ["photo", "photo & video"],
+  "icons": [
+    {
+      "src": "/favicon-16x16.png",
+      "sizes": "16x16",
+      "type": "image/png"
+    },
+    {
+      "src": "/favicon-32x32.png",
+      "sizes": "32x32",
+      "type": "image/png"
+    },
+    {
+      "src": "/apple-touch-icon.png",
+      "sizes": "180x180",
+      "type": "image/png"
+    },
+    {
+      "src": "/android-chrome-192x192.png",
+      "sizes": "192x192",
+      "type": "image/png"
+    },
+    {
+      "src": "/android-chrome-512x512.png",
+      "sizes": "512x512",
+      "type": "image/png"
+    }
+  ],
   "start_url": "/",
-  "display": "fullscreen"
-}
+  "display": "standalone",
+  "background_color": "#ffffff",
+  "theme_color": "#ffffff",
+  "description": "A non-invasive local photo viewer with a focus on speed and simplicity."
+}