added workflow for buildx

.github/workflows/build.yml

@@ -0,0 +1,25 @@
+name: build
+
+on:
+  push:
+    paths:
+      - ".github/workflows/build.yml"
+      - 'Changes'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: crazy-max/ghaction-docker-buildx@v3
+        with:
+          buildx-version: v0.4.1
+      - run: echo ${{ secrets.DOCKER_PASSWORD }} | docker login -u ${{ secrets.DOCKER_USERNAME }} --password-stdin
+      - run: git submodule update --init
+      - run: |
+          docker buildx build \
+            --push \
+            --platform=linux/arm64,linux/amd64 \
+            -f=docker/alpine/Dockerfile \
+            -t=${{ github.repository }} \
+            .