Add command line UI

[bertob]

Since actual support node infrastructure is still a ways off, we need some kind of short-term hack to get always-online nodes. One easy way to do this would be to just run the app on a server and keep the document open.

Two things are needed for this:

• A command line option to join documents (so you can easily join documents over SSH)
• A way to keep all documents syncing in the background, rather than just the one that's currently open

What I'm imagining is something like this:

Join new document

flatpak run cx.modal.Reflection --join 1c99b44a8586db20c02b7c2125fb6b874142e0a423bb03300fbfe5d4e3aeb019

Delete document

flatpak run cx.modal.Reflection --delete 1c99b44a8586db20c02b7c2125fb6b874142e0a423bb03300fbfe5d4e3aeb019

Run and sync all documents in the background

flatpak run cx.modal.Reflection --sync-all

If we wanted to get fancy with it we could have a --list command that shows a list of device IDs with some information on the doc (number of peers, size, last synced?), or even an --open command that allows seeing the content of a document. These are not required for the super basic use case though :)