Refactor `list` component

[ruipenso]

The list component should accept parameters to generate various list types, e.g.,

@mixin ucss-list($style) {
  padding-left: 0;

  list-style: none;

  @if ("inline" == $style) {
    > li {
      display: inline-block;
    }
  }

  @if ("fit" == $style) {
    // ...
  }
}

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