告诉iphone的safari浏览器：这个网站对应的是哪个app
<meta name="apple-itunes-app" content="app-id=589796322" />
参考：
https://segmentfault.com/q/1010000000171226
https://developer.apple.com/library/content/documentation/AppleApplications/Reference/SafariWebContent/PromotingAppswithAppBanners/PromotingAppswithAppBanners.html
