add github ci build image

.github/workflows/build-ci.yml

@@ -0,0 +1,63 @@
+name: build witness and relayer images
+
+on:
+  push:
+    branches: [ "master" ]
+    tags: [ 'v*.*.*' ]
+  pull_request:
+    branches: [ "master" ]
+
+env:
+  REGISTRY: ghcr.io
+
+jobs:
+  build_image:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        name: ["witness","relayer"]
+        include:
+          - name: witness
+            image_name: iotubeproject/witness
+            dockerfile: Dockerfile.witness
+          - name: relayer
+            image_name: iotubeproject/relayer
+            dockerfile: Dockerfile.relayer
+    permissions:
+      contents: read
+      packages: write
+      id-token: write
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
+      - name: Setup Docker buildx
+        uses: docker/setup-buildx-action@v2
+
+      - name: Log into registry ${{ env.REGISTRY }}
+        if: github.event_name != 'pull_request'
+        uses: docker/login-action@v2
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract Docker metadata
+        id: meta
+        uses: docker/metadata-action@v4
+        with:
+          images: ${{ env.REGISTRY }}/${{ matrix.image_name }}
+
+      - name: Build and push Docker image ${{ matrix.image_name }}
+        id: build-and-push
+        uses: docker/build-push-action@v4
+        with:
+          context: ./witness-service
+          platforms: linux/amd64, linux/arm64
+          file: ./${{ matrix.dockerfile }}
+          push: ${{ github.event_name != 'pull_request' }}
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          outputs: type=image,name=${{ env.REGISTRY_IMAGE }},name-canonical=true