Zarr append for datasets (non-reference)

[mavaylon1]

Motivation

What was the reasoning behind this change? Please explain the changes briefly.

This supports appending to zarr arrays. This does not cover the edge case for dataset of references. This has the base tests for append_data. There are more tests (TBD) in hdmf-zarr that incorporate the full IO process.

How to test the behavior?

Show how to reproduce the new behavior (can be a bug fix or a new feature)

Checklist

• Did you update CHANGELOG.md with your changes?
• Does the PR clearly describe the problem and the solution?
• Have you reviewed our Contributing Guide?
• Does the PR use "Fix #XXX" notation to tell GitHub to close the relevant issue numbered XXX when the PR is merged?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.78%. Comparing base (7426275) to head (57a0981).
Report is 28 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #1136      +/-   ##
==========================================
- Coverage   88.79%   88.78%   -0.02%     
==========================================
  Files          45       45              
  Lines        9774     9778       +4     
  Branches     2776     2777       +1     
==========================================
+ Hits         8679     8681       +2     
- Misses        778      780       +2     
  Partials      317      317              

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[stephprince]

small suggestion otherwise looks good to me!