LibWeb: Add port blacklist for ResourceLoader::load

`ResourceLoader::load` now rejects URLs which specify a `port`
associated with network services known to be vulnerable to
inter-protocol exploitation.

Fixes #1735

Libraries/LibWeb/ResourceLoader.h

@@ -55,6 +55,7 @@ private:
 
     Protocol::Client& protocol_client() { return *m_protocol_client; }
     RefPtr<Protocol::Client> m_protocol_client;
+    bool is_port_blocked(int port);
 };
 
 }