Add GitHub action to assign reviewers on PR created by Dependabot

[jnmt]

Description

This PR adds a GitHub action to assign reviewers to PRs created by Dependabot. CODEOWNERS file can automatically assign the ScalarDL team as reviewers to any pull request created, but it also assigns reviewers for the backport PRs, which is sometimes noisy. So, we use this action, the same as ScalarDB.

Related issues and/or PRs

• Update scheduled vulnerability check and Dependabot configuration #284
• Add GitHub action to assign reviewers on PR created by Dependabot scalardb#2694
• Fix Action to assign reviewers for Dependabot PRs scalardb#2958

Changes made

• Add GitHub action to assign reviewers on PR created by Dependabot

Checklist

The following is a best-effort checklist. If any items in this checklist are not applicable to this PR or are dependent on other, unmerged PRs, please still mark the checkboxes after you have read and understood each item.

• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation to reflect the changes.
• I have considered whether similar issues could occur in other products, components, or modules if this PR is for bug fixes.
• Any remaining open issues linked to this PR are documented and up-to-date (Jira, GitHub, etc.).
• Tests (unit, integration, etc.) have been added for the changes.
• My changes generate no new warnings.
• Any dependent changes in other PRs have been merged and published.

Additional notes (optional)

N/A

[gemini-code-assist]

Note

Gemini is unable to generate a summary for this pull request due to the file types involved not being currently supported.

[Copilot]

Pull Request Overview

This PR adds a GitHub Actions workflow to automatically assign the ScalarDL team as reviewers when Dependabot creates pull requests, providing a more targeted alternative to using CODEOWNERS which can be noisy for backport PRs.

• Introduces a new GitHub Actions workflow triggered when PRs are opened by Dependabot
• Uses GitHub CLI to assign scalar-labs/scalardl team as reviewers
• Utilizes a personal access token for authentication

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

[choplin]

LGTM!

[feeblefakie]

LGTM! Thank you!