much simpler bundling with rollup, also generate separate ESM and CJS files

src/index.d.ts

@@ -1,10 +1,8 @@
-export as namespace darkMode;
-
-export interface DarkModeOptions {
+interface DarkModeOptions {
   toggle?: HTMLElement;
   classes?: { dark: string, light: string };
   default?: string;
   storageKey?: string;
 }
 
-export function init(options?: Partial<DarkModeOptions>): void;
+export function init(options?: DarkModeOptions): void;

src/index.js

@@ -1,6 +1,6 @@
 "use strict";
 
-const initializeDarkMode = function (options) {
+const init = function (options) {
   // { toggle, classes: { light, dark }, default, storageKey }
   options = options || {};
 
@@ -101,4 +101,4 @@ const isStorageAvailable = function () {
   }
 };
 
-module.exports.init = initializeDarkMode;
+export { init };