title: Setting multiple parameters on breakpoint in MUI v5
body: <p>In MUI v4 I was able to set multiple style parameters on a single media query using something like the following:</p>
  <pre><code> [theme.breakpoints.up('xs')]: {
        width: 100px,
        color: green,
      },
   [theme.breakpoints.up('md')]: {
        width: 400px,
        color: blue,
      },
  </code></pre>
  <p>In MUI v5, I can set them individually on a component with the <code>sx</code> prop, in a relatively convenient way:</p>
  <pre><code>...
  sx={{
    width: {xs:'100px', md:'400px'},
    color: {xs: 'green', md:'blue'}
  }}
  </code></pre>
  <p>However I would like to be able to achieve the same type of functionality as in v4, where multiple params can be adjusted under a single breakpoint. It seems like the control has been inverted, and while this is often useful, I'd like to be able to use the original version as well. Is this possible?</p>