add docker build CI

Author: Prabhat1308

Diff for: .github/workflows/prod.yml

@@ -37,4 +37,15 @@ jobs:
             run: cargo clippy --release --features arkworks 
           #- name: Format check (verbose)
           #  run: cargo fmt -- --check --verbose $(find . -name '*.rs' -not -path './src/protobuf/*')
-        
+          
+          # New steps for Docker build
+          - name: Set up Docker Buildx
+            uses: docker/setup-buildx-action@v1
+          - name: Build Docker image
+            uses: docker/build-push-action@v2
+            with:
+              context: .
+              push: false
+              tags: drand:latest
+              cache-from: type=gha
+              cache-to: type=gha,mode=max