enhance usage of the open graph protocol

[lunika]

We use the open graph protocol on this site. This protocol allow a page to become a rich object in a social graph. This protocol is also used by social network to display a published link.

twitter also have its own metadata and while we only use twitter social network we also use them : https://developer.twitter.com/en/docs/tweets/optimize-with-cards/guides/getting-started.html

All the metadata are managed in _layouts/layout.html file.

More metadata can be used to display more information on twitter for example.
Here is the actual render:

idea to enhance it :

• add an image using the og:image metadata. It is also possible to add many more information on this image: http://ogp.me/#structured
• allow to override a default image in each post
• add a default description for every page
• allow to override the default description in each post