add book
POST https://postman-library-api.glitch.me/books
Request Body
{"title"=>"One Hundred Years of Solitude", "author"=>"Gabriel García Márquez", "genre"=>"fiction", "yearPublished"=>1967}
POST https://postman-library-api.glitch.me/books
{"title"=>"One Hundred Years of Solitude", "author"=>"Gabriel García Márquez", "genre"=>"fiction", "yearPublished"=>1967}