Include Gitea action to build Docker image

.gitea/workflows/build.yml

@@ -0,0 +1,33 @@
+name: Build Nginx-based docker image
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+jobs:
+  build-static-assets:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+      
+      - name: Login to the private Docker registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ secrets.PRIVATE_REGISTRY_HOST }}
+          username: ${{ secrets.PRIVATE_REGISTRY_USERNAME }}
+          password: ${{ secrets.PRIVATE_REGISTRY_TOKEN }}
+        
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          push: ${{ github.event_name != 'pull_request' }}
+          tags: |
+            ${{ secrets.PRIVATE_REGISTRY_HOST }}/${{ env.GITHUB_REPOSITORY }}:latest
+          cache-from: type=registry,ref=user/app:latest
+          cache-to: type=inline