Add PWA, service worker and Web Push

- Use new notification request/opt-in flow for push
- Implement unsubscribing
- Implement muting
- Implement emojis in title
- Add iOS specific PWA warning
- Don’t use websockets when web push is enabled
- Fix duplicate notifications
- Implement default web push setting
- Implement changing subscription type
- Implement web push subscription refresh
- Implement web push notification click

server/server.yml

@@ -38,6 +38,16 @@
 #
 # firebase-key-file: <filename>
 
+# Enable web push
+#
+# Run ntfy web-push-keys to generate the keys
+#
+# web-push-enabled: true
+# web-push-public-key: ""
+# web-push-private-key: ""
+# web-push-subscriptions-file: ""
+# web-push-email-address: ""
+
 # If "cache-file" is set, messages are cached in a local SQLite database instead of only in-memory.
 # This allows for service restarts without losing messages in support of the since= parameter.
 #