Finalise move of ThemeDefinition object type to Drupal module

[dpi]

Fixes #63

[codecov-commenter]

Codecov Report

❌ Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 98.11%. Comparing base (09c3452) to head (f212bbf).

Files with missing lines	Patch %	Lines
src/Attribute/ObjectType/Slots.php	66.66%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main      #68      +/-   ##
============================================
+ Coverage     97.08%   98.11%   +1.03%     
+ Complexity      246      232      -14     
============================================
  Files            38       35       -3     
  Lines           514      478      -36     
============================================
- Hits            499      469      -30     
+ Misses           15        9       -6     

☔ 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.