[FEATURE REQUEST] Empty state placeholders

[celarye]

Preflight Checklist

• I have read and I agree to follow the support disclaimer.
• I am sure that my feature request has nothing to with third party extensions.
• I am using the latest available Paperback version (currently 0.8).
• I have searched the issue tracker for a feature request that matches the one I want to file, without success.

What type of Apple device is the feature request for?

All device types

Describe the feature

This is a tracking issue for empty state placeholders in 0.9.

• The Navbar > Browse list on macOS and iPadOS when no extensions with discover section intents are installed.
• The Home view > Edit Sections view when no entries have been added to the home screen.
• The Search view when no extensions with search result intents are installed.
• The Updates view when no titles have received updates.
• The Library view > Collections without any titles.
• The Library view > Download Queue view when nothing is or has been downloaded.
• The Migrate view when no extensions are installed.
• The Settings view > Backup and Restore view when no backups have been made.
• The Source Migration title list view when there are no titles to migrate.
• The Title view > Description when a short or no description is present still show the Expand button.

These don't all need placeholders, some some of these views should maybe instead maybe not be accessible in those cases.

Needs verification:

• The Settings view > Search Filters view when the extension doesn't define any.

Feature Motivation

Some views can be confusing when there is no data to show. In those cases a placeholder (e.g. icon and or message) needs to be shown

Anything Else?

No response