I once met a person that never drank water, only soft drinks. It’s not the unhealthiness of this that disturbed me, but the fact they did it without the requisite paperwork.
Unlike those disorganised people I have a formal waiver. I primarily drink steam and crushed glaciers.
Read-only, or the ability to edit filenames & upload files?
Read only: as per other answers here, basically any HTTP server. The easiest one I know would be darkhttpd, because it requires no config files and can be run without root.
Read write: I like WFM https://github.com/tenox7/wfm