Storybook fix dark mode (#4865)

preview has now also a dark background & added a one click change theme
button

<img width="994" alt="Bildschirmfoto 2024-04-06 um 18 27 45"
src="https://github.com/twentyhq/twenty/assets/48770548/95f12617-e48f-4492-9b51-13410aff43ee">

packages/twenty-ui/.storybook/preview.tsx

@@ -0,0 +1,22 @@
+import { ThemeProvider } from '@emotion/react';
+import { Preview } from '@storybook/react';
+import { useDarkMode } from 'storybook-dark-mode';
+
+import { THEME_DARK, THEME_LIGHT } from '../src/theme/index';
+
+const preview: Preview = {
+  decorators: [
+    (Story) => {
+      const mode = useDarkMode() ? 'Dark' : 'Light';
+
+      const theme = mode === 'Dark' ? THEME_DARK : THEME_LIGHT;
+      return (
+        <ThemeProvider theme={theme}>
+          <Story />
+        </ThemeProvider>
+      );
+    },
+  ],
+};
+
+export default preview;