fix(pwa) move manifest to the root

It must be served from the same origin, so we need to bypass the CDN we use for
meet.jit.si. See the code comments for the rationale on the workaround.

debian/jitsi-meet-web.install

 connection_optimization	/usr/share/jitsi-meet/
 resources/robots.txt	/usr/share/jitsi-meet/
 resources/*.sh			/usr/share/jitsi-meet/scripts/
-pwa-worker.js /usr/share/jitsi-meet/
+pwa-worker.js			/usr/share/jitsi-meet/
+manifest.json			/usr/share/jitsi-meet/

index.html

 
     <link rel="apple-touch-icon" href="images/apple-touch-icon.png">
     <link rel="stylesheet" href="css/all.css">
-    <link rel="manifest" href="static/pwa/manifest.json">
+    <link rel="manifest" id="manifest-placeholder">
+
     <script>
+        // Dynamically generate the manifest location URL. It must be served from the document origin, and we may have
+        // the base pointing to the CDN. This way we can generate a full URL which will bypass the base.
+        document.querySelector('#manifest-placeholder').setAttribute('href', window.location.origin + '/manifest.json');
+
         document.addEventListener('DOMContentLoaded', () => {
             if (!JitsiMeetJS.app) {
                 return;

static/pwa/manifest.json → manifest.json

   "name": "Jitsi Meet",
   "icons": [
     {
-      "src": "icons/icon192.png",
+      "src": "static/pwa/icons/icon192.png",
       "type": "image/png",
       "sizes": "192x192"
     },
     {
-      "src": "icons/icon512.png",
+      "src": "static/pwa/icons/icon512.png",
       "type": "image/png",
       "sizes": "512x512"
     },
     {
-      "src": "icons/iconMask.png",
+      "src": "static/pwa/icons/iconMask.png",
       "sizes": "512x512",
       "type": "image/png",
       "purpose": "maskable"