Debounce site builder lambda

[jpsim]

From jpsim.com/awspics:

Another related problem is that for every new image in the source bucket, two are created in the resized bucket, each one invoking the site builder function. Not only that, but if I upload an album with lots of pictures all in one shot, the site will be rebuilt twice for each picture! 🙀

Unfortunately, S3 buckets can only have a single notification per event type, so we can't trigger both the resize and site builder functions when new objects are created on the source bucket.

I think the solution here would involve publishing S3 events to SNS or SQS and "debouncing" the site builder lambda, but again... #complexity.