Pass the homeserver's base URL to Element Call (#9429)

This will allow Element Call to perform media repo lookups, for example for avatars.

src/models/Call.ts

@@ -636,6 +636,7 @@ export class ElementCall extends Call {
             userId: client.getUserId()!,
             deviceId: client.getDeviceId(),
             roomId: groupCall.getRoomId()!,
+            baseUrl: client.baseUrl,
             lang: getCurrentLanguage().replace("_", "-"),
         });
         // Currently, the screen-sharing support is the same is it is for Jitsi