Automation of repository whitelist

[TheTrunk]

Is your feature request related to a problem? Please describe. Manual checking of images takes time, we need to create a both, github action that would automate the process

Describe the solution you'd like

• check whitelisted image pr only alters repositories.json
• check that repository is added at the end of an array
• check that no other repository is removed
• check that ONLY ONE repository is added - for more repositories more PRs!
• check indentation, spacing, linting (double quotations, one space etc.)
• check that image is a valid image present on public docker hub and satisfies flux constrains (image size limit)
• Run the image inside VM, create POC for flux devs to determine if image is safe (aka no prohibited content etc.)