This implements the option to choose directories when uploading files via the Web UI (The most important part of #52).
When you choose a directory, its file and sub-directory structure will be maintained.
Tested with the latest Safari, Firefox, and Chrome.
Additionally, the Deno version was updated, which required some accessibility improvements as well.
This is a WIP for advanced file sharing, but I won't pursue this for now since using symlinks in the file system works for me, and this is adding a ton of complexity I don't want or need right now.
