Adding `Clipboard Diff` plugin to c.json

First time submitting a sublime plugin :+1:

Very simple usage - compares the selection vs the clipboard and uses difflib to compute a diff and then outputs the diff to a new scratch view.

Typically when I  compare small chunks of data within a file I end up copying the `from` and `to` chunks to new files and then diff said files - this is sort of tedious and is remedied by this plugin.

Cheers!