Add OpenGraph & Twitter Card markup

[Andy Mabbett]

The Wikidata page, to pick a random example, at: https://www.wikidata.org/wiki/Q15136093 includes in its header the markup:

<meta property="og:title" content="Andy Mabbett"/>
<meta name="description" content="Wikipedian, author"/>
<meta property="og:description" content="Wikipedian, author"/>
<meta name="twitter:card" content="summary"/>
<meta property="og:image" content="https://upload.wikimedia.org/wikipedia/commons/thumb/9/9c/Andy_Mabbett%2C_GLAMcamp_Amsterdam%2C_Netherlands%2C_IMG_1324_edit.jpg/1200px-Andy_Mabbett%2C_GLAMcamp_Amsterdam%2C_Netherlands%2C_IMG_1324_edit.jpg"/>

However, the equivalent page: https://tools.wmflabs.org/reasonator/?q=Q15136093&lang=en does not.

Such markup improves the display when URLs are shared on social media. Please add it to Reasonator.

[Magnus Manske]

Reasonator is a JavaScript-only site, the HTML code is the same for every page, but the <meta> tags need to be in the HTML, so no can do.

(see e.g. https://twittercommunity.com/t/dynamically-adding-meta-tags-using-javascript-or-jquery-twitter-cards/22896 )

[Magnus Manske]

Fixed with #65e4d9b