Docs for blob storage limitations and performance

[stevekrouse]

The limitations would come from cloudflare r2.

The performance is also r2 so maybe they have notes on it or we can investigate ourselves and report on our docs.

[tmcw]

Doesn't seem like R2 has documented their key limitations, which makes me think that they're going to be the same as S3: https://docs.aws.amazon.com/AmazonS3/latest/userguide/object-keys.html