Strange date for directories

[jpds]

I noticed that a strange last-modified date is displayed for directories when this module is used with a Garage cluster (files are fine):

Perhaps instead a - could be displayed for this case?

[jpds]

Hmm, having taken a look at the codebases - this needs to be fixed here: https://github.com/caddyserver/caddy/blob/03f703a00e006a1e53a2eaf5f4e33a1b3a5e4237/modules/caddyhttp/fileserver/browse.html#L976-L991

I do not however have an alternative S3 implementation to double check if a modified date is returned on AWS for directories before submitting a PR to fix this.