message: fixed theme provider in a plugin test
diff: import React from 'react';
  import { render } from '@testing-library/react';
  import ExampleComponent from './ExampleComponent';
  +import { ThemeProvider } from '@material-ui/core';
  +import { BackstageTheme } from '@spotify-backstage/core';
  describe('ExampleComponent', () => {
  it('should render', () => {
  - const rendered = render(<ExampleComponent />);
  + const rendered = render(
  + <ThemeProvider theme={BackstageTheme}>
  + <ExampleComponent />
  + </ThemeProvider>
  + );
  expect(rendered.getByText('Welcome to {{ id }}!')).toBeInTheDocument();
  });
  });
  