treeForStyles(tree) {
    if (!tree) {
      return tree;
    }

    return new Funnel(tree, {
      destDir: 'app/styles',
      annotation: `Addon#treeForStyles (${this.name})`,
    });
  }
Returns the tree for all style files

    @public
    @method treeForStyles
    @param {Tree} tree The tree to process, usually `app/styles/` in the addon.
    @return {Tree} The return tree has the same contents as the input tree, but is moved so that the `app/styles/` path is preserved.