As of the latest version you can now add additional CSS and JS files to the voyager master blade without having to copy or modify the blade file itself removing potential manual migration headaches later on. The CSS and JS files are added after any Voyager assets so you can override styles and functionality comfortably.
This is all handled via the voyager.php config file:
// Here you can specify additional assets you would like to be included in the master.blade
The path will be passed to Laravels asset function.