feat: 🎸 support allenai/c4 dataset
See https://github.com/huggingface/datasets/issues/2859 and https://github.com/huggingface/datasets-preview-backend/issues/17
feat: 🎸 support allenai/c4 dataset: See https://github.com/huggingface/datasets/issues/2859 and https://github.com/huggingface/datasets-preview-backend/issues/17