title: Sass manipulate with @content
body: <p>Is it possible to manipulate with <code>@content</code> magic variable in SASS?
  I would like to replace some stuff in here before output.
  Or maybe can I fill some variable with it?</p>
  <p>The conclusion is that, I want to make an mixin <code>@important</code> that create both versions. Important, and no-important.</p>
  <p><strong>Input</strong></p>
  <pre><code>.test {
    @include important {
      color: red;
      text-align: left;
    }
  }
  </code></pre>
  <p><strong>Expected output</strong></p>
  <pre><code>.test {
    color: red;
    text-align: left;
  }
  .test-i {
    color: red !important;
    text-align: left !important;
  }
  </code></pre>