feat: add nostr.band relay for better bookmark coverage

- Add wss://relay.nostr.band to relay list
- Increase relay diversity for better bookmark discovery
- nostr.band is a popular relay with good event coverage

This should improve the chances of finding bookmarks
across different relay networks.

src/App.tsx

@@ -31,7 +31,8 @@ function App() {
     const relayUrls = [
       'wss://relay.damus.io',
       'wss://nos.lol', 
-      'wss://relay.snort.social'
+      'wss://relay.snort.social',
+      'wss://relay.nostr.band'
     ]
     
     // Connect to relays