webrtc: fix endless loading in Firefox (#4707)

Co-authored-by: aler9 <46489434+aler9@users.noreply.github.com>

internal/servers/webrtc/publish_index.html

@@ -411,7 +411,7 @@ const loadValuesFromQuery = () => {
   }
 };
 
-window.addEventListener('DOMContentLoaded', () => {
+window.addEventListener('load', () => {
   if (navigator.mediaDevices === undefined) {
     setMessage(`can't access webcams or microphones. Make sure that WebRTC encryption is enabled.`);
     return;

internal/servers/webrtc/read_index.html

@@ -80,7 +80,7 @@ const loadAttributesFromQuery = () => {
   defaultControls = video.controls;
 };
 
-window.addEventListener('DOMContentLoaded', () => {
+window.addEventListener('load', () => {
   loadAttributesFromQuery();
 
   new MediaMTXWebRTCReader({