Improve social sharing metadata

[lukestokes]

It should have the right tags for Facebook, Twitter, and the like. Here's what I see in Discord compare to the old site:

If possible, it would be great to customize the meta data per page.

[slyon]

The code for this meta data is here: https://github.com/eosdac/eosdacio-website/blob/master/_includes/head.html#L12

Customizing the meta data per page should be possible, even if it is a little inconvenient with the translations (i.e. for having localized meta data).