[feature] Generic container workflow

[ianlewis]

A container workflow similar to the generic workflow that allows users to build a container themselves in the user workflow and then generate provenance for it.

• Add container generator workflow (Add a generic container workflow #471)
• Pre-submit test ([feature] pre-submit test for container workflow #604)
• e2e tests ([feature] e2e tests for container generator workflow #603)
• Documentation
  • Basic usage (Add a generic container workflow #471)
  • [docs] Verifying provenance with Kyverno #389
  • [docs] Verification with sigstore-policy-controller #491

[datosh]

Estimates in README.md re container workflow might need an update.

• Build states to be expected Sept
• Generator states to be expected Aug-Sept

Do you have an estimate or a planned next minor release of this project?

As far as I can see, the core implementation is done, but docs & e2e are missing. I'd be open to helping out with e2e tests or integrating this into my project and providing early feedback. Would that be helpful? Any specific issues I could take a look at?