Thank you so much for your comments!  I implemented your many
suggestions wrt. the code.  I must say I didn't use to have all the
backquotes but then I read somewhere that you should prefer

  `(,x ,y)

over

  (list x y)

and so I replaced all the instances of the latter with the former.  I
probably misunderstood the "advice".

I also added the .elpaignore, removed the .info file and added a short
description.txt file to serve as readme.