Upcoming major improvements

Stuff that would be cool to get done and is well within out capacity. Please vote if you have favourites here!

• automagically run combine in dask tree reduction mode #255
• split to subchunk utility for uncompressed data. #251
• concatenate from subchunks for irregular inputs and primitive sharding support
• coords generation (e.g., FITS WCS, geoTIFF bounding boxes) for flexible xarray indexes (partial: #192 )
• parquet storage (from preffs) #277 with
  • lazy loading
  • sorted key partitioning
• subsampling and multiscale pyramid generation
• checksums or other UUIDs for remote files, to check for changes
• linked zarr/numcodecs: allow for read context to be passed to codec and storage layer, so that we can, for instance, apply a different scale to a cube at each pane https://github.com/zarr-developers/zarr-python/pull/1131
• consolidate (nearly) adjoining reads in ReferenceFileSystem as is done in fsspec.parquet https://github.com/fsspec/filesystem_spec/pull/1063

This is a broad roadmap covering several unchecked features, including irregular subchunk concatenation, parquet storage, multiscale generation, checksums, and linked codec/storage context. Start by selecting one item and finding its existing implementation or a focused follow-up issue; the relevant files, tests, and definition of done are not identified here.