Make embedding on IM a richer experience (add og:image)

htdocs/index.html

@@ -9,6 +9,10 @@
     <meta name="description" content="We collect, maintain and care for localization of material from the LQDN GAFAM campaign. CC0 licensed and a friendly community.">
     <meta name="keywords" content="gafam, information, localization">
 
+    <meta property="og:title" content="The GAFAM resource toolkit"/>
+    <meta property="og:description" content="We collect, maintain and care for localization of material from the LQDN GAFAM campaign. CC0 licensed and a friendly community."/>
+    <meta property="og:image" content="https://gafam.info/static/img/gafam-english.jpg"/>
+
     <!-- Let browser know website is optimized for mobile -->
     <meta name="viewport" content="width=device-width, initial-scale=1"/>