Download recursively a capsule
Add the ability to download recursively from a given URI, like
wget --mirror, for backups, mirror sites, etc. We can build that on the fact that Agunua already can parse a gemtext and return the list of links. We shoud limit it to one capsule and not follow outgoing links.
Does it require the ability to handle
robots.txt? Wget does it but it can go to external sites, which is more dangerous.
Attention security with the local file names: URIs can have tricks like
.". in order to allow local clobbering of existing files.