title: tidyr::pivot_wider() reorder column names grouping by `name_from`
body: <p>I would like to reorder the columns grouping by <code>names_from</code> instead of <code>values_from</code>, here is my minimal example:</p>
  
  <pre><code>mtcars %&gt;% 
  tidyr::pivot_wider(names_from = gear, values_from = c(vs, am, carb)) 
  </code></pre>
  
  <p>output:</p>
  
  <pre><code>    mpg   cyl  disp    hp  drat    wt  qsec  vs_4  vs_3  vs_5  am_4  am_3  am_5 carb_4 carb_3 carb_5
    &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt;  &lt;dbl&gt;  &lt;dbl&gt;  &lt;dbl&gt;
  1  21       6   160   110  3.9   2.62  16.5     0    NA    NA     1    NA    NA      4     NA     NA
  2  21       6   160   110  3.9   2.88  17.0     0    NA    NA     1    NA    NA      4     NA     NA
  3  22.8     4   108    93  3.85  2.32  18.6     1    NA    NA     1    NA    NA      1     NA     NA
  </code></pre>
  
  <p>Here is what I want the output:</p>
  
  <pre><code>   mpg   cyl  disp    hp  drat    wt  qsec  vs_4  am_4 carb_4  vs_3  am_3 carb_3  vs_5  am_5 carb_5
    &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt;  &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt;  &lt;dbl&gt; &lt;dbl&gt; &lt;dbl&gt;  &lt;dbl&gt;
  1  21       6   160   110  3.9   2.62  16.5     0     1      4    NA    NA     NA    NA    NA     NA
  2  21       6   160   110  3.9   2.88  17.0     0     1      4    NA    NA     NA    NA    NA     NA
  </code></pre>
  
  <p>Thanks in advance!</p>