V4 UI beta changes

[ilike2burnthing]

Dark mode, Custom Formats, and probably a lot of minor changes.

Sonarr v4 - Beta

After months of development and over 100 commits Sonarr v4 is ready for beta testers. There are a number of major changes and even more minor changes. Some of the changes are considered breaking changes and as DB migrations are not backwards compatible. Thanks to everyone that contributed, especially Qstick and ta264 for helping port over a number of changes from Radarr. Highlights v2 API has been removed Upgraded to .NET 6, mono is no longer supported Custom Formats, replacing Preferred Word…