feat!: change package requirements

- Configure as ES module
- Add svelte as peerDependency
- add Vite and vite-preprocess to inline imported SCSS

vite.config.js

@@ -0,0 +1,11 @@
+const config = {
+  css: {
+    preprocessorOptions: {
+      scss: {
+        additionalData: '@use "src/variables.scss" as *;',
+      },
+    },
+  },
+};
+
+export default config;