Docs should distinguish when to use paper-menu vs paper-listbox

[maria-le]

What are the differences between these two elements and when should we use one and not the other?

See this cross-post.

[indolering]

Relevant discussion on the evolution of paper-menu in #83.

[mercmobily]

This is my 2c ... I also left it as a comment to the Youtube video.

This is my own private list of differences between paper-menu and paper-listbox:

paper-menu:

• Comes with paper-menu-shared-styles
• Has paper-sub-menu
• Has extra styling option to make it disabled
• Has mixins for selected and focussed items

Also, both of them have the "multi" option, so I am not sure that's a huge difference.
Finally, the code is amazingly similar. I don't think I'd keep paper-listbox in the repo, frankly...