Add experimental GitHub Action

Author: tarleb

.github/workflows/debian.yaml

@@ -0,0 +1,48 @@
+name: Image Builder
+
+on:
+  push:
+    paths:
+      - 'debian/*'
+      - 'versions.md'
+      - 'LICENSE'
+      - '**/bookworm/*'
+  pull_request:
+    # Build, but don't push on pull requests
+
+jobs:
+  build:
+    name: Build
+    runs-on: ubuntu-latest
+    needs: configure
+
+    strategy:
+      fail-fast: false
+      matrix:
+        stack: ${{ fromJSON( needs.configure.outputs.stacks ) }}
+        version: ${{ fromJSON( needs.configure.outputs.pandoc-version ) }}
+
+    env:
+      PUSH_IMAGE: ${{ github.repository == 'pandoc/dockerfiles' &&
+                      (github.ref == 'refs/heads/main' ||
+                       github.ref_type == 'tag' ||
+                       github.event_name != 'pull_request') }}
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Login to Docker Hub
+        uses: docker/login-action@v3
+        if: ${{ env.PUSH_IMAGE }}
+        with:
+          username: ${{ secrets.DOCKER_HUB_USERNAME }}
+          password: ${{ secrets.DOCKER_HUB_TOKEN }}
+
+      - name: Build and maybe push image
+        uses: docker/build-push-action@v5
+        with:
+          file: '3.5/bookworm/Dockerfile'
+          context: '.'
+          push: ${{ env.PUSH_IMAGE }}
+          tags: '3.5-debian'