title: October CMS disallowed file types
body: <p>I'm trying to upload a .pptx file to the media library in October CMS and I'm getting an error because the filetype is not allowed. I have tried using the following suggestion from Stackoverflow:</p>
  
  <p><code>'fileDefinitions' =&gt; [
      'assetExtensions' =&gt; array_merge(FileDefinitions::get('assetExtensions'), ['docx']), ],</code></p>
  
  <p>But I get an error message about FileDefinitions class not existing. I have also tried another suggestion of adding to a fileTypes array in /config/cms.php but that doesn't work either as this way of including files seems to be gone.</p>
  
  <p>The October CMS git repo had a pull request which added a file type to the source code but I feel this is not a great idea as different users have different needs and the system would have to be updated every time someone wants a new file type added! Anyway, does anyone know a good way that works of simply adding a new file type the the allow file types array?</p>
  
  <p>Seems like it should be a simple config setting but for the life of me I can't find any working reference.</p>