add dataobjects.dtype to DatasetMeta

[kmuehlbauer]

Description

This will help downstream packages to retrieve the H5 datatype of the Dataset. Needed for h5netcdf/Pyfive integration.

Closes #111

Before you get started

• ☝ Create an issue to discuss what you are going to do

Checklist

• This pull request has a descriptive title and labels
• This pull request has a minimal description (most was discussed in the issue, but a two-liner description is still desirable)
• Unit tests have been added (if codecov test fails)
• Any changed dependencies have been added or removed correctly (if need be)
• If you are working on the documentation, please ensure the current build passes
• All tests pass

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.29%. Comparing base (4512046) to head (ab9969f).
⚠️ Report is 182 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #112      +/-   ##
==========================================
+ Coverage   72.73%   73.29%   +0.56%     
==========================================
  Files          11       11              
  Lines        2505     2543      +38     
  Branches      382      390       +8     
==========================================
+ Hits         1822     1864      +42     
+ Misses        580      576       -4     
  Partials      103      103              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.