add feed:// since firefox and safari support it, throw a better error than "fall-through in case"

basis/urls/urls.factor

@@ -212,11 +212,15 @@ PRIVATE>
     [ [ host>> ] [ port>> ] bi <inet> ] [ protocol>> ] bi
     secure-protocol? [ <secure> ] when ;
 
+ERROR: no-protocol-found protocol ;
+
 : protocol-port ( protocol -- port )
     {
         { "http" [ 80 ] }
         { "https" [ 443 ] }
+        { "feed" [ 80 ] }
         { "ftp" [ 21 ] }
+        [ no-protocol-found ]
     } case ;
 
 : ensure-port ( url -- url' )