feat(web): add pwa icons and manifest (#72)

rich installation requires screenshot and a description but this is more than enough

web/index.html

···
 
     <link rel="preload" as="font" type="font/woff2" href="/static/media/InterVariable.c504db5c06caaf7cdfba.woff2" crossorigin>
 
+    <link rel="manifest" href="/manifest.json" />
+
     <style>
       /**
        * Minimum styles required to render splash.

web/manifest.json

···
+{
+  "short_name": "Catsky",
+  "icons": [
+    {
+      "src": "/favicon.ico",
+      "sizes": "64x64 32x32 24x24 16x16",
+      "type": "image/x-icon"
+    },
+    {
+      "src": "/pwa-192.png",
+      "type": "image/png",
+      "sizes": "192x192"
+    },
+    {
+      "src": "/pwa-512.png",
+      "type": "image/png",
+      "sizes": "512x512"
+    }
+  ],
+  "start_url": "/",
+  "display": "standalone",
+  "id": "social.catsky", 
+  "theme_color": "rgb(30, 30, 46)",
+  "background_color": "rgb(30, 30, 46)"
+}