Many of the builder methods add duplicate query parameters

[Nordeast]

There are some more user friendly ways to construct this library that I think should be added. For instance the implementation for many of the builder methods simply just keep appending the same query parameter to the list even if a param has already been added before. Ideally the library would find and update the parameter rather than add a duplicate. Consider this code:

var query = QueryBuilder<SitemapItem>.New.ContentTypeIs("myType");
query.Limit(100);
query.Limit(200);
Console.WriteLine(query.Build()); 

// outputs
// ?content_type=myType&limit=100&limit=200

The desired outcome would be ?content_type=myType&limit=200 as adding the parameter on twice produces an invalid query and allowing the the limit to be updated can simply some code.