Add help message to stale message

Author: Garulf

.github/workflows/stale.yml

@@ -20,7 +20,7 @@ jobs:
     steps:
       - uses: actions/stale@v9
         with:
-          stale-issue-message: 'This issue is stale because it has been open 45 days with no activity. Remove stale label or comment or this will be closed in 5 days.'
+          stale-issue-message: 'This issue is stale because it has been open ${{ env.days-before-stale }} days with no activity. Remove stale label or comment or this will be closed in ${{ env.days-before-stale }} days.\n\nAlternatively this issue can be kept open by adding one of the following labels:\n${{ env.exempt-issue-labels }}'
           days-before-stale: ${{ env.days-before-stale }}
           days-before-close: ${{ env.days-before-close }}
           days-before-pr-close: -1