CI: build: login to registry step

.forgejo/workflows/build.yaml

@@ -21,6 +21,13 @@ jobs:
       - name: Run basic test (bootstrap)
         run: pytest -s tests/basic.py
 
+      - name: Log in to container registry
+        uses: redhat-actions/podman-login@v1
+        with:
+          registry: ${{ vars.REPOSITORY }}
+          username: ${{ secrets.REGISTRY_USER }}
+          password: ${{ secrets.REGISTRY_PASSWORD }}
+
       - name: Build container
         uses: actions/buildah-build@v1
         with: