S3 support

[the-maldridge]

It would be nice to support writing the man pages to a remote object store using an S3 compatible API. This would enable the reading of the data to happen on a clock, and then to asynchronously refresh the data the CGI application is serving using something like rclone again running on a timer.

[ericonr]

maldridge | you would probably want to approach it by setting up an interface for listing and writing files
maldridge | then implement the standard file backend, and additionally implement an S3 backend
maldridge | that way we could use either approach