Integrated file sharing for iPad

I would really like to be able to go into an iPad app (e.g. Goodnotes), hit "Export" and have KeyBase show up as a target, so that I can export directly to a folder there. My use case is signing financial documents (signing like with my Apple Pencil and my hand-written signature), and I need a way to sign it and share the document back. I would love to do it through KeyBase. Obviously, first you need to support files at all on iPad, but I wanted to make sure that when you do, it's well-integrated into the iOS ecosystem so that apps can see it as a target for export (and you need to be able to open files in KeyBase and send them to the appropriate app as well).

I assume that this feature is already on your backlog somewhere, so if there's some other place I can just +1 that feature and watch progress, please let me know (I did search the github issues but didn't find anything).

The issue names no files, tests, or entry points. Start by reviewing the existing iPad/iOS file support and the platform's export and open-in integrations. Done means files can be exported from apps into Keybase folders and opened from Keybase in the appropriate app.

Written by the indexing model from the issue text.