matrix-ntfy: enable WebSocket proxying

roles/matrix-nginx-proxy/templates/nginx/conf.d/matrix-ntfy.conf.j2

@@ -27,6 +27,8 @@
 			{# Generic configuration for use outside of our container setup #}
 			proxy_pass http://127.0.0.1:80;
 		{% endif %}
+		proxy_set_header Upgrade $http_upgrade;
+		proxy_set_header Connection "upgrade";
 
 		proxy_set_header Host $host;
 		proxy_set_header X-Forwarded-For {{ matrix_nginx_proxy_x_forwarded_for }};