Add Twitter Card to pages

[woecifaun]

:warning: Starting to work on this issue? Please indicate it in a comment below to prevent many people working on same stuff at the same moment. Thanks.

In order to improve communication via Twitter by adding photos, it should be great to add Twitter card to:

• home page
• contribution page

https://dev.twitter.com/cards/overview

[woecifaun]

:sweat_drops: working on it :smile_cat: