Expose the selection and yank link function to have direct access to it.

Hi,

Thanks for keysnail, firefox the emacs way! Lovin' it!
Thanks for HoK, way faster than mouseless ever was!

Could you consider the yank-mode a worthy functionality to add?

Actions done:
- create the yank function
- expose it through a yank mode
- renamed the anonymous function from the extended mode to use the yank function

Cheers,