Add docker release flow for gb200 (#8394)

.github/workflows/release-docker-gb200.yml

+name: Release Docker Images (GB200)
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - "python/sglang/version.py"
+  workflow_dispatch:
+
+jobs:
+  publish:
+    if: github.repository == 'sgl-project/sglang'
+    runs-on: ubuntu-latest
+    environment: 'prod'
+    steps:
+      - name: Delete huge unnecessary tools folder
+        run: rm -rf /opt/hostedtoolcache
+
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Login to Docker Hub
+        uses: docker/login-action@v2
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Build and Push
+        run: |
+          version=$(cat python/sglang/version.py | cut -d'"' -f2)
+          tag=v${version}-cu128-gb200
+
+          docker buildx build --platform linux/arm64 --output type=image,compression=zstd . -f docker/Dockerfile.gb200 --build-arg CUDA_VERSION=12.8.1 --build-arg BUILD_TYPE=blackwell -t lmsysorg/sglang:${tag} --no-cache
+          docker push lmsysorg/sglang:${tag}