title: Include categories custom fields in REST api
body: <p>I am working with Advanced custom fields, where I add an image selector for categories in wp - But I can't see the data in my JSON response for categories? 
  I have tried to use several plugins to do the same, but That haven't worked either - </p>
  
  <p>I am using ACF to rest plugin to include acf fields in the response, which works fine on custom post types - where it creates an array field called "acf" 
  This field is not created in my categories though - Am i missing a function to use it in taxonomies? </p>
  
  <p>examples.</p>
  
  <pre><code>domain.com/wp-json/wp/v2/recipies (a custom post type)
  </code></pre>
  
  <p>returns everything including acf.</p>
  
  <pre><code>domain.com/wp-json/v2/categories (a texonomy)
  </code></pre>
  
  <p>returns all of the categories, but nothing about acf</p>
  
  <pre><code>domain.com/wp-json/wp/v2/categories/37 (a single category)
  </code></pre>
  
  <p>returns the category but nothing about acf.</p>
  
  <pre><code>domain.com/wp-json/wp/v2/categories/37?_embed[0] (way of getting all embedded stuff)
  </code></pre>
  
  <p>Does not show acf</p>
  
  <p>Hope that you can put me on the right path.</p>