Add a context menu with discover.el

Here it is !
I added a simple listing of the commands.
Note that I didn't specify a default keybinding (I just said how to do it in the readme).
So this feature requires discover.el. Will you add it as a dependency of yafolding or say in the readme to install it ? I think it's easier to add it as a dependency and that doesn't have any drawbacks.
  I tested it with evaluating the whole buffer and calling M-x yafolding-discover.
  Tell me what you think !