in apis/scaladoc-1.0.0/scripts/theme.js [14:20]
function toggleDarkTheme(isDark) {
currentlyDark = isDark
// this triggers the `:root.theme-dark` rule from scalastyle.css,
// which changes the values of a bunch of CSS color variables
document.documentElement.classList.toggle("theme-dark", isDark);
supportsLocalStorage && localStorage.setItem(settingKey, isDark);
}