Extend style definition syntax

[jeluard]

The style key should support multiple style element definition and a way to provide other style attribute (like media or title).

A potential syntax could be:

(defwebcomponent my-component
  :style '({:media "screen"
            :title "My screen style"
            :content "a {background: red;}"}
           {:media "print"
            :title "My print style"
            :content [:a {:background "green"})}

[jeluard]

List syntax is now available for both style and content