Added support for FB public posts and videos using FB's developer documentation

[kopos]

For facebook at https://developers.facebook.com/docs/plugins/oembed-endpoints

Tested with urls

• https://www.facebook.com/SSRajamouli/photos/a.110306842412362.15991.110106192432427/1074721632637540/?type=3
• https://www.facebook.com/publicenemy/posts/1283615724996488
• https://www.facebook.com/shakira/photos/a.142708799559.109364.5027904559/10155214244304560/?type=3&permPage=1
• https://www.facebook.com/OpinionPolls/posts/1447334938641596
• https://www.facebook.com/youtube/videos/10155481607356754/?permPage=1