Group Dependabot updates

[samdark]

Replicates the Dependabot grouping configuration from yiisoft/package-template so GitHub Actions updates are grouped into a single PR and Composer dependency updates are grouped into a single PR.

[Copilot]

Pull request overview

Note

Copilot couldn't run its full agentic review because no GitHub Actions runner was available. Make sure your repository has a runner available to run Copilot's review, or add a copilot-setup-steps.yml file specifying one with the runs-on attribute. See the docs for more details.

Adds Dependabot grouping so GitHub Actions and Composer dependency updates are consolidated into single PRs per ecosystem, matching yiisoft/package-template’s setup.

Changes:

• Added a groups section for the github-actions ecosystem to group all action updates.
• Added a groups section for the composer ecosystem to group all Composer dependency updates.
• Fixed YAML structure/indentation in the Composer update config (schedule/versioning-strategy placement).

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (cc91b17) to head (827cd1f).

Additional details and impacted files

@@             Coverage Diff             @@
##              master      #282   +/-   ##
===========================================
  Coverage     100.00%   100.00%           
  Complexity       837       837           
===========================================
  Files             91        91           
  Lines           2265      2265           
===========================================
  Hits            2265      2265           

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