New features

Custom theming for views panes is now a custom class, as it should have been. Improves layout slightly. Light theme is probably stable now; I'm considering this a release candidate.

First draft of light version

• Moved configuration to admin/config/development/performance/quicklink
• Renamed and migrated configuration
• Enabled Intersection Observer polyfill by default.
• Vertical tabs interface
• Issue #3021759 by btully: Option to only load library on certain node types
• Display warning on Quicklink settings form if debug mode is enabled.
• Issue #3022882 by andyg5000, mherchel: Add option to prevent Quicklink prefetching when
  sessions are present.

Base theme

• Issue #3 "Unknown "dd" function"
• Removed outdated documentation.
• Added new variable main_layout_attributes contains empty object Attribute() for main layout modifiers on demand.

Starter theme