Read test resources to be synced from _viash.yaml.

[rcannood]

The demultiplex repo has a specification for where test resources are located and where they should be synced to: https://github.com/viash-hub/demultiplex/blob/main/_viash.yaml#L9-L12

I'd be cool if we could allow sync-and-cache-s3 to pick up this field or create a new action which is able to do so.