Add Gitea Actions workflow to publish container image on tags

Build the root Dockerfile and push to gitea.kosmos.org/5apps/liquor-cabinet, tagged with the pushed git tag name.

.gitea/workflows/publish-image.yml

@@ -0,0 +1,32 @@
+name: Publish container image
+
+on:
+  push:
+    tags: ["*"]
+
+env:
+  REGISTRY: gitea.kosmos.org
+  IMAGE: gitea.kosmos.org/5apps/liquor-cabinet
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - uses: builtin:checkout
+      # The automatic job token (GITEA_TOKEN / secrets.GITHUB_TOKEN) cannot
+      # publish to Gitea's package registry, so use a personal access token
+      # (with package write access) supplied via repository/org secrets.
+      - name: Log in to the container registry
+        run: |
+          echo "${{ secrets.REGISTRY_TOKEN }}" | docker login "$REGISTRY" \
+            --username "${{ secrets.REGISTRY_USERNAME }}" --password-stdin
+      - name: Build and push
+        run: |
+          set -e
+          # Git tag names can contain characters that are invalid in Docker
+          # tags (e.g. "/"), so sanitize the ref-derived tag.
+          tag="$(echo "$GITHUB_REF_NAME" | tr '/' '-')"
+          docker build -t "$IMAGE:$tag" .
+          docker push "$IMAGE:$tag"