[CI/Build] Add bot to close stale issues and PRs

[russellb]

This PR adds configuration to run the actions/stale github
action that closes stale issues and PRs.

Further discussion is on the issue.

Closes #9435

Signed-off-by: Russell Bryant [email protected]

[github-actions]

👋 Hi! Thank you for contributing to the vLLM project.
Just a reminder: PRs would not trigger full CI run by default. Instead, it would only run fastcheck CI which starts running only a small and essential subset of CI tests to quickly catch errors. You can run other CI tests on top of those by going to your fastcheck build on Buildkite UI (linked in the PR checks section) and unblock them. If you do not have permission to unblock, ping simon-mo or khluu to add you in our Buildkite org.

Once the PR is approved and ready to go, your PR reviewer(s) can run CI to test the changes comprehensively before merging.

To run CI, PR reviewers can do one of these:

• Add ready label to the PR
• Enable auto-merge.

🚀

[hmellor]

This tutorial seems like a good template for us to use https://docs.github.com/en/actions/use-cases-and-examples/project-management/closing-inactive-issues

[hmellor]

This is a very valuable PR for the health of the issue and pull request counters!

I've just left a few comments about word choices and removing a few lines that aren't 100% necessary.

[russellb]

This is a very valuable PR for the health of the issue and pull request counters!

I've just left a few comments about word choices and removing a few lines that aren't 100% necessary.

Thanks for the review! I applied all of the suggested edits except the one about the action reference (tag vs commit hash).