Need to add an automated workflow to build kconfig image referenced in the kernel README.md file

[detiber]

Expected Behaviour

The kernel readme references a non-existing kconfig image: https://github.com/tinkerbell/hook/blob/master/kernel/README.md

We should automate the building/publishing of this image based on changes to the kernel version we are targeting.

This will require:

• a new quay.io repository to be created (quay.io/tinkerbell/hook-kconfig)
• The readme to reference the new image
• A new push job added to the github workflows to build/push the hook-kconfig image when needed