Add harmony-yggdrasil Docker images

.github/workflows/docker.yml

@@ -67,3 +67,56 @@ jobs:
           tags: |
             ghcr.io/${{ env.GHCR_NAMESPACE }}/harmony:latest
             ghcr.io/${{ env.GHCR_NAMESPACE }}/harmony:${{ env.RELEASE_VERSION }}
+
+  yggdrasil:
+    name: Yggdrasil image
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Get release tag & build flags
+        if: github.event_name == 'release' # Only for GitHub releases
+        run: |
+          echo "RELEASE_VERSION=${GITHUB_REF#refs/*/}" >> $GITHUB_ENV
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+      - name: Login to GitHub Containers
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Build Yggdrasil image
+        if: github.ref_name == 'main' || github.event_name == 'workflow_dispatch'
+        id: docker_build_monolith
+        uses: docker/build-push-action@v3
+        with:
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+          context: .
+          file: Dockerfile.yggdrasil
+          platforms: ${{ env.PLATFORMS }}
+          push: true
+          tags: |
+            ghcr.io/${{ env.GHCR_NAMESPACE }}/harmony-yggdrasil:${{ github.ref_name }}
+
+      - name: Build release Yggdrasil image
+        if: github.event_name == 'release' # Only for GitHub releases
+        id: docker_build_monolith_release
+        uses: docker/build-push-action@v3
+        with:
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+          context: .
+          file: Dockerfile.yggdrasil
+          platforms: ${{ env.PLATFORMS }}
+          push: true
+          tags: |
+            ghcr.io/${{ env.GHCR_NAMESPACE }}/harmony-yggdrasil:latest
+            ghcr.io/${{ env.GHCR_NAMESPACE }}/harmony-yggdrasil:${{ env.RELEASE_VERSION }}