* Add dark mode

* Add a new config option to control dark mode. Supported modes: auto, dark, light
Optimize dark mode css

* Implement dark mode using multiple css files

* Add Dracula theme for HighlighJS

Based on https://github.com/dracula/highlightjs/blob/master/dracula.css

* Update laravel-debugbar-dark-mode.css

Co-authored-by: Barry vd. Heuvel <barryvdh@gmail.com>