попробовал сборку

.gitea/workflows/demo.yaml

@@ -6,4 +6,10 @@ jobs:
   Explore-Gitea-Actions:
     runs-on: ubuntu-latest
     steps:
-      - run: docker build ./ -t platformer
+      - name: Checkout 
+        uses: actions/checkout@v2 # Required to mount the Github Workspace to a volume 
+      - uses: https://github.com/addnab/docker-run-action@v3
+        with:
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_PASSWORD }}
+          run: docker build ./ -t platformer