v0.99.7-beta: playlist cover images in sidebar + bugfixes

• New: playlist cover images are now shown in the sidebar.
• Change: per-track embedded art downloading is back and enabled by default but heavily optimised. A new onboarding wizard will help you pick the right mode.
• Change: editing album art, artist avatars and playlist covers will now propagate to the rest of the app instantly.
• Fix: restore in-memory image cache codepath.
• Fix: song-level stickers not loading, interfering with dynamic playlists.
• Fix: stickers capability degrading to songs-only in presence of albums with insufficient tagging for sticker query.

Pull Requests

• fix: handle cached image load failures correctly by @aaravrav in #345
• Show playlist images in sidebar + hotfix song-level stickers not loading by @htkhiem in #348
• Implement per-file cover downloading option + startup wizard by @htkhiem in #344
• More proper implementation of embedded art priority by @htkhiem in #349

Full Changelog: v0.99.6-beta-1...v0.99.7-beta