title: Loading fonts to customize Material-UI theme in Next.js not working
body: <p>I'm trying to add different fonts to my theme.js while using Material-UI in Next.js. It's been surprisingly difficult to figure out how. </p>
  
  <p>I've tried using fontfaceobserver as suggested here(<a href="https://github.com/zeit/next.js/issues/512" rel="noreferrer">https://github.com/zeit/next.js/issues/512</a>), but can't get the theme to update. Here's my theme.js file: </p>
  
  <pre><code>const theme = createMuiTheme({
    typography: {
      fontFamily: [
        'Raleway','Roboto Condensed',
      ].join(','),
      fontWeight: 700,
      h1:{
        fontFamily: 'Raleway',
        fontWeight: 700,
      }
    },
  });
  </code></pre>
  
  <p>The font for my h1 doesn't change :(</p>