chore: build mult-platform image (#4)

Build multi-platform image per https://docs.docker.com/build/ci/github-actions/multi-platform/

Author: nicksieger

.github/workflows/docker.yaml

@@ -38,6 +38,7 @@ jobs:
       - name: Build and push
         uses: docker/build-push-action@v4
         with:
+          platforms: linux/amd64,linux/arm64
           push: true
           tags: |
             controlplane/netassertv2-l4-client:${{ github.ref_name }}