chore: Add workflow to remove untagged images

Resolves: #82

.github/workflows/stale-image-clean.yml

@@ -0,0 +1,27 @@
+name: stale-image-clean
+
+on:
+  schedule:
+    - cron: '5 4 * * 5'
+  workflow_dispatch:
+
+defaults:
+  run:
+    shell: bash
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: clang-format
+
+jobs:
+  clean-untagged-images:
+    name: Clean untagged images
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/setup-go@v2
+        with:
+          go-version: '1.17'
+      - name: Install ghcr-cleaner
+        run: go install github.com/jidicula/ghcr-cleaner
+      - name: Run ghcr-cleaner
+        run: ghcr-cleaner --token "${{ secrets.GITHUB_TOKEN }}" --packagename clang-format