fix(cd): latest tag added to release (#39)

# Problem
latest tag missing

# Solution
adding latest tag https://stackoverflow.com/a/73109667

Co-authored-by: Aditya Sadalage <aditya.sadalage@gmail.com>

Author: skrdgraph

.github/workflows/cd-dgraph-lambda.yml

@@ -34,4 +34,4 @@ jobs:
         run: |
           docker buildx create --name builder --driver docker-container
           docker buildx use builder
-          docker buildx build -t dgraph/dgraph-lambda:${{ env.DGRAPH_LAMBDA_RELEASE_VERSION }} --push --platform=linux/arm64,linux/amd64 .
+          docker buildx build -t dgraph/dgraph-lambda:${{ env.DGRAPH_LAMBDA_RELEASE_VERSION }} -t dgraph/dgraph-lambda:latest --push --platform=linux/arm64,linux/amd64 .