* Add nvim as a diff tool for getplugs plugin

* Comment out `is_cmd_exists()`

* Add nvim diff tool for diffs plugin

* Add $EDITOR to nuke plugin for editing/reading text file format

* Modify diff command to fix CircleCI failures

* Fix getplugs prompt

* Allow nuke to use custom $PAGER

See https://kristaps.bsd.lv/lowdown/

Replaces the following environment variables:
- NNN_USE_EDITOR
- NNN_IDLE_TIMEOUT