Manifest and Basic Authentication

Hi Weston,

thanks for the excellent work on the plugin.
I use Basic Authentication on my Site (via HTPASSWD).
I get an error, when the manifest should get written in pwa/wp-includes/class-wp-web-app-manifest.php.
Maybe you could add something like:
<link rel=”manifest” href=”<?php echo esc_url( rest_url( self::REST_NAMESPACE . self::REST_ROUTE ) ); ?>” crossorigin=”use-credentials”>
to the creation code.

Thanks in advance.
Best regards.
Christoph.