title: TailwindCSS - adding fontSize
body: <p>TailwindCSS 1.2.0</p>
  <p>What I'm doing wrong? if I add fontSize as below text-7xl doesn't show up as the new optional value and text-6xl disappear.</p>
  <pre class="lang-js prettyprint-override"><code>module.exports = {
      important: true,
      theme: {
          fontFamily: {
              'theme-f1': ['&quot;Oswald&quot;', &quot;sans-serif&quot;],
              'theme-f2': ['&quot;Lora&quot;', &quot;serif&quot;],
              'theme-f3': ['&quot;Bebas Kai&quot;', &quot;sans-serif&quot;],
              'theme-f4': ['&quot;Open Sans&quot;', &quot;sans-serif&quot;],
          },
          fontSize: {
              '7xl': '7rem',
          },
          extend: {
              colors: {
                  'theme-c1': '#006c32',
                  'theme-c1-b': '#6c8213',
                  'theme-c2': '#000000',
                  'theme-c3': '#ffffff',
              }
          },
      },
      variants: {
          letterSpacing: ['responsive', 'hover', 'focus'],
      },
      plugins: [],
  }
  
  </code></pre>