feat(pwa): make the app installable

Manifest, gamepad icon (also the new favicon, instead of
the Vite logo), iOS meta tags and the tab title
ToBePlayed. No service worker, so a deploy never meets
an old cached bundle. The title bar color follows
light and dark mode. The README also lists adding a
game by name.

public/manifest.webmanifest

@@ -0,0 +1,16 @@
+{
+  "id": "/",
+  "name": "ToBePlayed",
+  "short_name": "TBP",
+  "description": "Your game backlog: Steam library, games from other platforms, and what to play next.",
+  "start_url": "/dashboard",
+  "scope": "/",
+  "display": "standalone",
+  "background_color": "#09090b",
+  "theme_color": "#09090b",
+  "icons": [
+    {"src": "/icon-192.png", "sizes": "192x192", "type": "image/png", "purpose": "any"},
+    {"src": "/icon-512.png", "sizes": "512x512", "type": "image/png", "purpose": "any"},
+    {"src": "/icon-maskable-512.png", "sizes": "512x512", "type": "image/png", "purpose": "maskable"}
+  ]
+}