upload_mimes allow doc and docx

function upload_mimes ( $mimes = array() ) {
  // Allow SVG
  $mimes['svg'] = 'image/svg+xml';
  $mimes['docx'] = 'application/vnd.openxmlformats-officedocument.wordprocessingml.document';
  $mimes['doc'] = 'application/msword';
  return $mimes;
}
add_filter( 'upload_mimes', 'upload_mimes' );