finish implementing path parameters

SimpleHttpServer/Types/PathParameterAttribute.cs

@@ -19,6 +19,10 @@ public sealed class PathParameterAttribute : Attribute {
             throw new ArgumentException($"'{nameof(name)}' must not contain spaces.", nameof(name));
         }
 
+        if (!uint.TryParse(name[1..], out _) && name != "$*") {
+            throw new ArgumentException($"'{nameof(name)}' must only consist of spaces or be exactly '$*'.", nameof(name));
+        }
+
         Name = name;
     }
 }