// allow SVG uploads
add_filter('upload_mimes', 'custom_upload_mimes');
function custom_upload_mimes ( $existing_mimes=array() ) {
	$existing_mimes['svg'] = 'image/svg+xml';
	return $existing_mimes;
}
function fix_svg() {
    echo '<style type="text/css">
          .attachment-266x266, .thumbnail img {
               width: 100% !important;
               height: auto !important;
          }
          </style>';
 }
 add_action('admin_head', 'fix_svg');