chore: update dependabot.yml with shared content

[holochain-release-automation2]

This PR updates dependeabot.yml with the content from the shared file in the hc-github-config repo.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: f230f30f-549e-4f2c-952a-ca4f837b3670

📥 Commits

Reviewing files that changed from the base of the PR and between 2023707 and d1459fa.

📒 Files selected for processing (1)

• .github/dependabot.yml

🚧 Files skipped from review as they are similar to previous changes (1)

• .github/dependabot.yml

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Walkthrough

Adds a Dependabot v2 configuration for weekly GitHub Actions updates and monthly npm updates. Both ecosystems scan all packages under the repository root and group version updates separately.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the Dependabot configuration update and its source as shared content.
Description check	✅ Passed	The description directly explains that dependabot.yml receives content from the shared hc-github-config file.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch chore/update-dependabot-yml

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[cocogitto-bot]

✔️ d1459fa - Conventional commits check succeeded.