Bundle json-mode in GNU Emacs

[notetiene]

I was wondering if contributors would like to integrate json-mode in the GNU Emacs distribution or at least include it in ELPA.

I saw that a version is available on ELPA and that the copyright notice is for Free Software Foundation, Inc.

@joshwnj, did you make an official copyright assignment to the FSF?

(By the way thanks for that project)