Piwigo Release note 2.10

Past release notes for piwigo are very compact and hard to read. With this in mind I redesigned the latest release note (2.10) so that we could distinguish more the titles from the paragraphs and the image captions. The previous versions also had a big menu that looked like a footer at the top of th page, I decided to get rid of this element, and put a mockup that showcases the new elements for piwigo 2.10.