chore: miscellaneous cleanup

- Update README documentation
- Update favicon configuration
- Enhance site metadata in Head.astro and consts.ts
- Refactor RSS feed generation logic in rss.xml.ts
- Adjust avatar schema to accept both URL and local paths in content.config.ts

public/site.webmanifest

@@ -1,19 +1,21 @@
 {
-  "name": "erudite",
-  "short_name": "erudite",
+  "name": "astro-erudite",
+  "short_name": "astro-erudite",
   "icons": [
     {
-      "src": "/android-chrome-192x192.png",
+      "src": "/web-app-manifest-192x192.png",
       "sizes": "192x192",
-      "type": "image/png"
+      "type": "image/png",
+      "purpose": "maskable"
     },
     {
-      "src": "/android-chrome-512x512.png",
+      "src": "/web-app-manifest-512x512.png",
       "sizes": "512x512",
-      "type": "image/png"
+      "type": "image/png",
+      "purpose": "maskable"
     }
   ],
-  "theme_color": "#121212",
-  "background_color": "#121212",
+  "theme_color": "#ffffff",
+  "background_color": "#000000",
   "display": "standalone"
-}
+}