[ENH] Add gallery highlight in the landing page

[acocac]

          My other comment relates to the landing page. I suggest steer users more directly towards the gallary, e.g., by showing 3-4 highlight gallary cards with a link to the full set (similar to https://sci.vision), or even merge the front page and gallary into one page. 

The gallary is really clear and my sense is that a user would instantly undertand what the EDSbook is all about - by comparison the current front page is a little text heavy and isn't as eye catching

Originally posted by @scotthosking in #139 (comment)