Add support for serving directory listing

[notthetup]

This adds a new option to the WebServer.add API called directoryListing, which allows directories to be listed over HTTP either

• using Content-Type: text/plain in which case the files in a directory will be listed as

boo.txt 12 1728272211249

• using Content-Type: application/json in which case the files in a directory will be listed as

[{"name":"boo.txt","size":12,"date":1728272211249}]

Also ,

• all the options are moved into a WebServerOptions object for future extension.
• directoryListing is ignored when serving resources from jars