Support Free alternatives to Dropbox on Lychee - e.g. Nextcloud, Syncthing

[OrcVole]

Enhancement

Lychee supports adding images from Dropbox. This is sweet, however Dropbox is non-Free.
I hope that Lychee could add the additional options of Free alternatives, like Nextcloud or Syncthing.

https://docs.nextcloud.com/server/19/developer_manual/api.html

https://docs.syncthing.net/

[d7415]

Nextcloud is similar, sure, but syncthing is a completely different tool.

For syncthing I'd recommend setting Lychee up to watch a folder that syncthing can sync to. (I've done this in the past)