Stale issue workflow

Add ci workflow to run on cronjob for labelling stale issues and closing issues labelled `S-stale` 7 days later.

**Additional context**

If issue also has `S-prevent-stale` label it should be left open

Ref: https://github.com/paradigmxyz/reth/blob/main/.github/workflows/stale.yml

Review the referenced .github/workflows/stale.yml and inspect the repository's .github/workflows directory for the appropriate entry point. The workflow should run on a cron schedule, label stale issues, close S-stale issues after 7 days, and leave issues with S-prevent-stale open.

Written by the indexing model from the issue text.