HiGlass Zarr DataFetchers

Plugin data fetchers for loading Zarr-based files in HiGlass, allowing genomic data to be stored in object stores like S3 instead of using higlass-server. Current version 0.6.0 (stable, released 2023). Supports multivec and bar track types. Requires manual registration with higlass-register. Key differentiator: enables serverless HiGlass deployment by fetching data directly from cloud storage.