Implement new DoES Visors logo

[afroleft]

We have a new identity here https://github.com/DoESLiverpool/covid19/issues/77#issuecomment-613325928

New domain is currently resolving but it will be visors.doesliverpool.com

[afroleft]

Tacking on:

• [x] Updating the favicon. I follow this guide for retina ready https://daringfireball.net/2013/01/retina_favicons
• [x] Updating the social share image in images/

[zarino]

Done! https://ppe.doesliverpool.com