Release 0.4.0

[mavaylon1]

Prepare for release of HDMF-Zarr [0.4.0]

Before merging:

• [x] Major and minor releases: Update package versions in requirements.txt, requirements-dev.txt, requirements-doc.txt, requirements-min.txt, and setup.py as needed
• [x] Check legal file dates and information in Legal.txt, license.txt, README.rst, docs/source/conf.py, and any other locations as needed
• [x] Update setup.py as needed
• [x] Update README.rst as needed
• [x] Update changelog (set release date) in CHANGELOG.md and any other docs as needed
• [x] Run tests locally including gallery tests, and inspect all warnings and outputs (pytest && python test_gallery.py)
• [x] Test docs locally by going into the docs directory and running the following: make clean && make html
• [x] Push changes to this PR and make sure all PRs to be included in this release have been merged
• [x] Check that the readthedocs build for this PR succeeds (build latest to pull the new branch, then activate and build docs for new branch): https://readthedocs.org/projects/hdmf-zarr/builds/

After merging:

1. Create release by following steps in docs/source/make_a_release.rst or use alias git pypi-release [tag] if set up
2. After the CI bot creates the new release (wait ~10 min), update the release notes on the GitHub releases page with the changelog
3. Check that the readthedocs "latest" and "stable" builds run and succeed
4. Update conda-forge/hdmf_zarr-feedstock with the latest version number and SHA256 retrieved from PyPI > HDMF-Zarr > Download Files > View hashes for the .tar.gz file. Re-render as needed

[codecov-commenter]

Codecov Report

All modified lines are covered by tests :white_check_mark:

Comparison is base (0be6b04) 85.92% compared to head (2438d5d) 85.92%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev #130 +/- ## ======================================= Coverage 85.92% 85.92% ======================================= Files 13 13 Lines 3189 3189 ======================================= Hits 2740 2740 Misses 449 449 ```

:umbrella: View full report in Codecov by Sentry.
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