Add OpenGraph headers

[Artoria2e5]

The Open Graph protocol enables developers to integrate their pages into the social graph. These pages gain the functionality of other graph objects including profile links and stream updates for connected users.

From Wikipedia, the free encyclopedia.
en.wikipedia.org/wiki/Facebook_Platform#Open_Graph_protocol

Open Graph can be also used by Sina Weibo.

Somehow like other <meta> tags, we should set the header to each article we post……

<!--Generate those automatically using PHP?
    Port detection can be removed in our case, and we can hard-encode SERVER_NAME.
    So it turns into 'https://portal.anthonos.org'.$_SERVER['REQUEST_URI'] -->
<meta property="og:url" content="<?='https://'.$_SERVER['SERVER_NAME'].$_SERVER['SERVER_PORT']!='443'?$_SERVER['SERVER_PORT']:''.$_SERVER['REQUEST_URI']?>"/>
<meta property="og:site_name" content="Anthon Open Source Community"/>
<!--And then RTFM. -->

I'm not sure if we can use Accept-Lang to tell users using different languages from each other. If so we can use the $lang array.

[MingcongBai]

Well if anyone would do this...

[Yexiaoxing]

Check http://ogp.me/ for documents.