Add config to hide logo-deep-linking on deeplinking page (#7346)

This adds the ability to configure hiding the logo on the deep linking page.
HIDE_DEEP_LINKING_LOGO defaults to false in the config.
The implementation also defaults to showing the logo if HIDE_DEEP_LINKING_LOGO
is missing from the config.

interface_config.js

@@ -101,6 +101,11 @@ var interfaceConfig = {
 
     GENERATE_ROOMNAMES_ON_WELCOME_PAGE: true,
 
+    /**
+     * Hide the logo on the deep linking pages.
+     */
+    HIDE_DEEP_LINKING_LOGO: false,
+
     /**
      * Hide the invite prompt in the header when alone in the meeting.
      */