ci: added build docker image and push to docker hub

.github/workflows/docker-build.yml

@@ -0,0 +1,56 @@
+name: Docker build on push
+env:
+  DOCKER_CLI_EXPERIMENTAL: enabled
+
+on:
+  push:
+    tags:
+      - '*'
+
+jobs:
+  build:
+    runs-on: ubuntu-20.04
+    name: Build and push sphinx swarm image 
+    env:
+      ACTIONS_ALLOW_UNSECURE_COMMANDS: true
+    steps:
+      - name: Check out from Git
+        uses: actions/checkout@v2
+      - name: Test env
+        run: echo "RELEASE_TAG=${GITHUB_REF#refs/*/}" >> $GITHUB_ENV
+      - name: Test print env
+        run: |
+          echo $RELEASE_TAG
+          echo ${{ env.RELEASE_TAG }}
+      - name: Login to Docker Hub
+        run: echo "${{ secrets.DOCKER_PASSWORD }}" | docker login -u "${{ secrets.DOCKER_USERNAME }}" --password-stdin
+      - name: Checkout project
+        uses: actions/checkout@v2
+      - name: Setup Docker buildx action
+        uses: crazy-max/ghaction-docker-buildx@v1
+        id: buildx
+        with:
+          buildx-version: latest
+          qemu-version: latest
+      - name: Show available buildx platforms
+        run: echo ${{ steps.buildx.outputs.platforms }}
+      - name: Cache Docker layers
+        uses: actions/cache@v2
+        id: cache
+        with:
+          path: /tmp/.buildx-cache
+          key: ${{ runner.os }}-buildx-${{ github.sha }}
+          restore-keys: |
+            ${{ runner.os }}-buildx-
+      - name: Test print env
+        run: |
+          echo $RELEASE_TAG
+          echo ${{ env.RELEASE_TAG }}
+      - name: Run Docker buildx
+        run: |
+          docker buildx build \
+          --cache-to "type=local,dest=/tmp/.buildx-cache" \
+          --platform linux/amd64,linux/arm/v7 \
+          --tag "${{ secrets.DOCKER_HUB_USER }}/sphinx-swarm:${{ env.RELEASE_TAG }}" \
+          --tag "${{ secrets.DOCKER_HUB_USER }}/sphinx-swarm:latest" \
+          --output "type=registry" ./