As an Administrator I would like to use ProxyResolver provided by LiipImagineBundle, ref: https://github.com/liip/LiipImagineBundle/blob/master/Resources/doc/cache-resolver/proxy.rst

For QA
After applying the changes, please configure image_host as following:

ezpublish:
    system:
        siteaccess:
            image_host: http://example.com

and try to load an article which contains the image. URL to the image should start with http://example.com instead of working local domain.