chore: add Renovate config #78

bcgov/actions-openshift has no Renovate config, so nothing keeps its workflow and composite-action dependencies current. bcgov/actions already has one.

It shows: .github/workflows/probe-runner-reachability.yml (added in #55) uses actions/upload-artifact@v4 and actions/download-artifact@v4, which are Node 20 releases. GitHub now forces them onto Node 24 with a deprecation warning. The latest releases are v7.0.1 and v8.0.1. Six actions/checkout@v7 refs are also tag-only rather than SHA-pinned.

Fix

• Add renovate.json matching bcgov/actions:

  {
    "$schema": "https://docs.renovatebot.com/renovate-schema.json",
    "extends": ["github>bcgov/renovate-config#2026.9.26"]
  }

• SHA-pin actions/upload-artifact and actions/download-artifact at their latest majors, with a # vX.Y.Z comment. Or let Renovate's first run do it.
• Confirm that Renovate opens its Dependency Dashboard and the first PRs.