Remaining TODOs for CUE schemas

[RagnarGrootKoerkamp]

• Add CUE to the docker image
• Add CI to vet all generators.yaml files in BAPCtools repo
• Add documentation on how to use the cue files in an editor. (This requires converting to json schema first; maybe see https://github.com/cue-lang/cue/discussions/663)
• Do we also want to have cue vet as part of bt validate? bt generate should pretty much validate the same but in a less structured way. (bt generate is slightly more lenient probably.)