Adding support for apps like Ulysses

[S0ulf3re]

I'm wanting to use my Nextcloud with Ulysses. However, when I try to add it a folder with it, the option to use Nextcloud is grayed out. Inferencing off of the data I've collected, this seems to be an issue with the way Nextcloud gathers data using the file provider extensions within iOS. Ulysses looks for enumerated contents, mainly because the app has a feature within it that allows you to add external folders. And Ulysses will allow you to edit any markdown file within said folder, and will also watch for new ones and ones that get removed.

Naturally, Ulysses works with apps including Working copy and Secure Shellfish, with the latter simply being an SFTP client. So I'm assuming it should be relatively easy for nextcloud to work the same since WebDAV just exposes the contents.