Added FindPlusPlus to repositories.json

Added [Find++ package][fpp] to package control listing.

This module adds commands from [Notepad++][npp] (e.g. `Find in current file`) as well as new ones (e.g. `Find in...`, `Find in project`).

[fpp]: https://github.com/twolfson/FindPlusPlus
[npp]: notepad-plus-plus.org