Add DF-SHOW

[roberthawdon]

Checklist for submitting a pull request to Terminals Are Sexy:

• [x] I have carefully read and comply with the Contributing Guidelines of this repo.
• [x] I have searched the PRs of this repo and believe that this is not a duplicate.

- **Title**: DF-SHOW - **Link**: https://github.com/roberthawdon/dfshow - **Category**: Tools and Plugins - **Description**: An interactive directory and file browser with a similar feel to the `ls` command.

[roberthawdon]

Additional endorsements:

Linux Today: https://www.linuxtoday.com/developer/df-show-a-terminal-file-manager-based-on-an-old-dos-application-181029061007.html

OS Technix: https://www.ostechnix.com/df-show-a-terminal-file-manager-based-on-an-old-dos-application/

Przystajnik (Polish): https://404.g-net.pl/2018/10/terminal-pogryzl-czlowieka-df-show/

[roberthawdon]

It has also been further endorsed on page 80 of the March issue of Linux Magazine (issue 220):

http://www.linux-magazine.com/Issues/2019/220/FOSSPicks

[k4m4]

Thanks! Could you also squash your commits into one? Apologies for the delayed response.

[roberthawdon]

Hi, apologies for the delay. That has been squashed as requested.