Add a GA workflow to prune workflow runs on GitHub

.github/workflows/prune-workflow-runs.yml

@@ -0,0 +1,28 @@
+name: Delete old workflow runs
+on:
+  workflow_dispatch:
+    inputs:
+      days:
+        description: 'Number of days.'
+        required: true
+        default: 30
+      minimum_runs:
+        description: 'The minimum runs to keep for each workflow.'
+        required: true
+        default: 6
+      delete_workflow_pattern:
+        description: 'The name or filename of the workflow. if not set then it will target all workflows.'
+        required: false
+
+jobs:
+  del_runs:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Delete workflow runs
+        uses: Mattraks/delete-workflow-runs@v2
+        with:
+          token: ${{ github.token }}
+          repository: ${{ github.repository }}
+          retain_days: ${{ github.event.inputs.days }}
+          keep_minimum_runs: ${{ github.event.inputs.minimum_runs }}
+          delete_workflow_pattern: ${{ github.event.inputs.delete_workflow_pattern }}