Add an exception to method 'whitelist_protocols' for url which started with '#'

This is to allow local link for markdown, actually a local link write with this syntax : '[anchor](#local_link)' produce this html code: http://#local_link

application/http/UrlUtils.php

@@ -73,7 +73,7 @@ function add_trailing_slash($url)
  */
 function whitelist_protocols($url, $protocols)
 {
-    if (startsWith($url, '?') || startsWith($url, '/')) {
+    if (startsWith($url, '?') || startsWith($url, '/') || startsWith($url, '#')) {
         return $url;
     }
     $protocols = array_merge(['http', 'https'], $protocols);