S3 + CloudFront directory indexer update v94

This package keeps directory listings and .directory-index.json cacheable for 365 days, while the S3 event updater Lambda invalidates affected CloudFront paths after creates, overwrites, and deletes.

Required updater Lambda environment variable:
  CLOUDFRONT_DISTRIBUTION_ID=YOUR_DISTRIBUTION_ID

Optional:
  ENABLE_CLOUDFRONT_INVALIDATION=true
  CLOUDFRONT_PATH_PREFIX=
  DIRECTORY_INDEX_CACHE_CONTROL=public, max-age=31536000, s-maxage=31536000, immutable

The updater Lambda package now requires both @aws-sdk/client-s3 and @aws-sdk/client-cloudfront. Use the package.json in s3-directory-index-updater/ when building the Lambda deployment zip.