WordPress: Allow upload of non-standard file types in the media library.

wordpress-mime-types.php

<?php 
// functions.php

/**
 * Allow upload of non-standard file types in the media library.
 *
 * @param  array $mime_types [default mime types].
 * @return array $mime_types [modified mime types].
 */
function mnet_upload_mime_types($mime_types) {
  if ( !isset($mime_types['webp']) ) {
    $mime_types['webp'] = 'image/webp';
  }
  if ( !isset($mime_types['svg']) && current_user_can('edit_posts') ) {
    $mime_types['svg'] = 'image/svg+xml';
  }
  return $mime_types;
}
add_filter('upload_mimes', 'mnet_upload_mime_types', 110, 1);