Blog: update stylesheet to match new FAIRsharing site

[allysonlister]

While I realize that this is not directly relevant to the FAIRsharing UI, it does have UI elements and therefore I've put the ticket here for lack of a better place.

Please could we update the stylesheet used for blog.fairsharing.org to have a closer match with the new FAIRsharing site? Just marked as a low priority, thank you!