fix(safari-ios): adding webcomponents-hi.js for webcomponets ready
fix(safari-ios): adding webcomponents-hi.js for webcomponets ready

Adding this polyfill because Safari needs only HTML imports for the old Webcomponents spec, so the webcomponents-loader must have this polyfill available for firing WebcomponentsReady event
PolymerX/polymer-skeleton,PolymerX/polymer-skeleton