This Lambda@Edge function tries to find the best bucket to serve static content because Cloudfront can't directly talk to an S3 multiregion access point.
This script assumes that there is a bucket with the name {BASE_NAME} in the region {FALLBACK_REGION}. The buckets in all
other regions are named like {BASE_NAME}-{region-name}.
Then deploy this function to us-east-1 and attach it to the Origin Request of your Cloudfront distribution.