ci: add manylinux-cache clean-up

Author: mayeut

.github/workflows/clean-cache.yml

@@ -0,0 +1,30 @@
+name: Clean image cache
+
+on:
+  workflow_dispatch:
+    inputs:
+      dry-run:
+        description: Dry Run
+        type: boolean
+        required: false
+        default: false
+  schedule:
+    - cron: "30 10 * * 3"  # At 10:30 on Wednesday.
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.sha }}
+  cancel-in-progress: false
+
+jobs:
+  cleanup:
+    if: github.repository == 'pypa/manylinux'
+    name: Clean image cache
+    runs-on: ubuntu-latest
+    permissions:
+      packages: write
+    steps:
+      - uses: dataaxiom/ghcr-cleanup-action@cd0cdb900b5dbf3a6f2cc869f0dbb0b8211f50c4 # v1.0.16
+        with:
+          package: manylinux-cache
+          delete-untagged: true
+          dry-run: (github.event_name == 'workflow_dispatch') && fromJSON(github.event.inputs.dry-run)