Add cross-validation support #44

Summary

Add support for cross-validation

What problem does this solve?

Add support for cross-validation:
a) on pre-defined folds
b) or generate folds when none are specified

Proposed solution

Add cv option to data_pipeline

Alternatives considered

No response

Related datasets or benchmarks

No response

References & supporting material

No response

How can you help?

• I am willing to contribute implementation work (code, configs, or docs).
• I can help validate the feature on my data / benchmarks.
• I am only proposing the idea.