title: Cannot override Material UI Typography fontWeight
body: <p>I just started using Material UI and learning to customize the default theme. I tried changing default palette color and it worked but overriding the typography property was not working.</p>
  <p>I am trying to fontWeight property of h3 variant. The default fontWeight for h3 variant is 400. I am changing it to 100 or 300 but it's not reflecting.</p>
  <p>Here is my code</p>
  <p><strong>Component.js</strong></p>
  <pre><code>return (
  
           &lt;Typography variant=&quot;h3&quot; color=&quot;secondary&quot;&gt;
                 Arc Development
           &lt;/Typography&gt;
      )
  </code></pre>
  <p><strong>theme.js</strong></p>
  <pre><code>import {createMuiTheme} from &quot;@material-ui/core&quot;;
  
  const arcBlue = &quot;#0B72B9&quot;;
  const arcOrange = &quot;#FFBA60&quot;;
  
  export default createMuiTheme({
      palette: {
          common: {
              blue: `${arcBlue}`,
              orange: `${arcOrange}`,
          },
          primary: {
              main: `${arcBlue}`
          },
          secondary: {
              main: `${arcOrange}`
          }
      },
      typography: {
          h3: {
              fontS: 0,
          }
      }
  });
  </code></pre>