Fix Websocket timeouts:

* defining a ping_interval in ConverseJS
* defining a longer c2s_close_timeout in Prosody configuration

conversejs/builtin.ts

@@ -138,6 +138,7 @@ window.initConverse = async function initConverse ({
     assets_path: assetsPath,
 
     authentication: 'anonymous',
+    ping_interval: 60, // must be set accordingly to c2s_close_timeout backend websocket settings
     auto_login: true,
     auto_join_rooms: [
       room

server/lib/prosody/config/content.ts

@@ -217,6 +217,7 @@ class ProsodyConfigContent {
     this.global.set('consider_bosh_secure', true)
     if (useWS) {
       this.global.set('consider_websocket_secure', true)
+      this.global.set('c2s_close_timeout', 65) // must be set accordingly with ConverseJS ping_interval
 
       // This line seems to be required by Prosody, otherwise it rejects websocket...
       this.global.set('cross_domain_websocket', [publicServerUrl])