Add option to implement krux sign a file created by

[qlrd]

see @odudex krux_file_signer.py

[qlrd]

This wont be implemented since I and @odudex planned to create a separate CLI/GUI application in another repo, ath the moment in:

• https://github.com/qlrd/krux-file-signer
• https://github.com/odudex/krux-file-signer