ci: add container publish workflow

.github/workflows/container.yml

@@ -0,0 +1,29 @@
+name: Publish bulk loader Docker container
+
+on:
+  workflow_dispatch:
+
+jobs:
+  build_and_push:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v4
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v4
+
+      - name: Build and push
+        uses: docker/build-push-action@v7
+        with:
+          context: ./bulk_loader
+          file: ./bulk_loader/Dockerfile
+          push: true
+          tags: ghcr.io/dathere/ckan_geoconnex_bulk_runner:latest
+          cache-from: type=gha,scope=ckan_geoconnex_bulk_runner
+          platforms: linux/amd64
+          cache-to: type=gha,mode=max,scope=ckan_geoconnex_bulk_runner