kctrl: Adding documentation for package authoring flow

[100mik]

Checklist:

• [x] Tutorial for packaging upstream release artifact
• [x] Tutorial for packaging from local directory
• [x] Command reference (separate PR: #509 )
  • [x] init
  • [x] release
  • [x] repo release
• [x] Quick guide on using repo release (Can be a part of command reference?)