[Enhancement] Document `context.imageReference` manifestList to check multi-arch images

### Description

Document `context.imageReference` manifestList to check multi-arch images

See:

https://github.com/kyverno/kyverno/blob/main/pkg/engine/context/loaders/imagedata.go#L139

https://github.com/kyverno/kyverno/pull/9883

https://github.com/kyverno/kyverno/issues/8273

### Slack discussion

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