[Misc]: Enable dependabot to help managing known vulnerabilities in dependencies

[fcanogab]

Anything you want to discuss about vllm.

Enable dependabot to help managing known vulnerabilities in dependencies. It would create PRs to update dependencies when needed and based on a configuration. There is a PR open (#1217), but it is for GitHub Actions and not for all dependencies.

Before submitting a new issue...

• Make sure you already searched for relevant issues, and asked the chatbot living at the bottom right corner of the documentation page, which can answer lots of frequently asked questions.

[github-actions]

This issue has been automatically marked as stale because it has not had any activity within 90 days. It will be automatically closed if no further activity occurs within 30 days. Leave a comment if you feel this issue should remain open. Thank you!

[github-actions]

This issue has been automatically closed due to inactivity. Please feel free to reopen if you feel it is still relevant. Thank you!