Add dandi:dandi-zarr-checksum digest

[dchiquito]

Add a new digest type dandi:dandi-zarr-checksum for representing the new zarr checksum digest.

[codecov]

Codecov Report

Merging #108 (f677479) into master (7e53e9f) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #108   +/-   ##
=======================================
  Coverage   96.35%   96.35%           
=======================================
  Files          16       16           
  Lines        1453     1453           
=======================================
  Hits         1400     1400           
  Misses         53       53           

Flag	Coverage Δ
unittests	96.35% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
dandischema/model_types.py	100.00% <ø> (ø)
dandischema/tests/test_models.py	95.55% <ø> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 7e53e9f...f677479. Read the comment docs.

[satra]

@jwodder - there appears to be a few CLI failures that seem unrelated to this change.

[jwodder]

@satra I believe those are all due to the latest release of dandi not including dandi/dandi-cli#854.

[satra]

thank you @jwodder

[jwodder]

@satra Could this be merged & released soon? The lack of this digest type value is one of the more concrete blockers for Zarr support in dandi-cli.