refactor: Improve typings for element-ui imports (no-changelog) (#4678)

* convert all stories to typescript

* stricter typing for element-ui imports

packages/design-system/.storybook/main.js

@@ -4,7 +4,7 @@ const path = require('path');
  * @type {import('@storybook/core-common').StorybookConfig}
  */
 module.exports = {
-	stories: ['../src/**/*.stories.mdx', '../src/**/*.stories.@(js|ts)'],
+	stories: ['../src/**/*.stories.mdx', '../src/**/*.stories.ts'],
 	addons: [
 		'@storybook/addon-links',
 		'@storybook/addon-essentials',

packages/design-system/.storybook/preview.js

@@ -1,11 +1,17 @@
 import './font-awesome-icons';
 import './storybook.scss';
 
+import ElementUI from 'element-ui';
 import lang from 'element-ui/lib/locale/lang/en';
 import locale from 'element-ui/lib/locale';
 
+import designSystemComponents from '../src/plugins/n8nComponents';
+
 import Vue from 'vue';
 
+Vue.use(ElementUI);
+Vue.use(designSystemComponents);
+
 locale.use(lang);
 
 // https://github.com/storybookjs/storybook/issues/6153