feature: CLI command to print unread entries

[chaulkie]

I would like an entry on my status bar that tells me the number of unread RSS entries I have waiting. All I need to get that working is the relevant info from Bulletty.

I'm proposing a command like bulletty unread, that will:

• Print the number of unread items.
• OR print a list of the unread items, one per line. Then for my own use-case it would be simple to just pipe that into wc.

[crocidb]

Hey @chaulkie,

That's an interesting idea. My next step would be creating a "virtual" category that stores the new/unread items. That can be a nice way to have a streamlined information about that without even having to open the TUI. Of course, that would update all the feeds before.

Let me try to implement the new/unread items this weekend and I'll see what can be done for this CLI command.

Thanks for putting the time to create the issue, I really appreciate that.