Release 3.6.1 (#869)

Prepare for release of HDMF [version]

### Before merging:
- [ ] Major and minor releases: Update package versions in `requirements.txt`, `requirements-dev.txt`,
  `requirements-doc.txt`, `requirements-min.txt`, `requirements-opt.txt`, `environment-ros3.yml`, and `setup.py` as needed
- [ ] Check legal file dates and information in `Legal.txt`, `license.txt`, `README.rst`, `docs/source/conf.py`,
  and any other locations as needed
- [ ] Update `setup.py` as needed
- [ ] Update `README.rst` as needed
- [ ] Update `src/hdmf/common/hdmf-common-schema` submodule as needed. Check the version number and commit SHA manually
- [ ] Update changelog (set release date) in `CHANGELOG.md` and any other docs as needed
- [ ] Run tests locally including gallery tests, and inspect all warnings and outputs
  (`pytest && python test_gallery.py`)
- [ ] Run PyNWB tests locally including gallery and validation tests, and inspect all warnings and outputs
  (`cd pynwb; python test.py -v > out.txt 2>&1`)
- [ ] Test docs locally by going into the `docs` directory and running the following: `make clean && make html`
- [ ] Push changes to this PR and make sure all PRs to be included in this release have been merged
- [ ] 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/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](https://github.com/hdmf-dev/hdmf/releases) with the changelog
3. Check that the readthedocs "latest" and "stable" builds run and succeed
4. Update [conda-forge/hdmf-feedstock](https://github.com/conda-forge/hdmf-feedstock) with the latest version number
   and SHA256 retrieved from PyPI > HDMF > Download Files > View hashes for the `.tar.gz` file. Re-render as needed

CHANGELOG.md

@@ -1,6 +1,6 @@
 # HDMF Changelog
 
-## HMDF 3.6.1 (upcoming)
+## HMDF 3.6.1 (May 18, 2023)
 
 ### Bug fixes
 - Fix compatibility with hdmf_zarr for converting string arrays from Zarr to HDF5 by adding logic to determine the dtype for object arrays. @oruebel [#866](https://github.com/hdmf-dev/hdmf/pull/866)