feat: support multiarch build for reloader (#1050)

Signed-off-by: liubo02 <liubo02@pingcap.com>

Author: liubog2008

.github/workflows/reloader-dockerhub.yaml

@@ -13,6 +13,9 @@ jobs:
       - name: Checkout code
         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
 
@@ -31,5 +34,6 @@ jobs:
         with:
           context: .
           file: reload/Dockerfile_buildx
+          platforms: linux/amd64,linux/arm64
           push: true
           tags: pingcap/tidb-monitor-reloader:${{ steps.vars.outputs.image_tag }}