message: Check if dark mode is enabled and toggle
  Storybook components are wrapped using a decorator in the storybook config. When rendering, useDarkMode() will let the component know which theme (dark/light) to thoose.
diff: import React from 'react';
  import { addDecorator } from '@storybook/react';
  -import { lightTheme } from '@backstage/theme';
  +import { lightTheme, darkTheme } from '@backstage/theme';
  import { CssBaseline, ThemeProvider } from '@material-ui/core';
  +import { useDarkMode } from 'storybook-dark-mode';
  addDecorator(story => (
  - <ThemeProvider theme={lightTheme}>
  + <ThemeProvider theme={useDarkMode() ? darkTheme : lightTheme}>
  <CssBaseline>{story()}</CssBaseline>
  </ThemeProvider>
  ));
  