Is it possible to append query values?

I read through the docs but couldn't find any information on how to append query values to my request. In my case, these are conditional, so some methods on the `Builder` struct would be great.

Sadly, simply appending them to the URL is not enough. The values have to be URL-encoded. A utility method similar to other crates would be great. It could take any `T: Serializable` and append the query values. `reqwest` and `ureq` provide this IIRC.

Thanks for the great library!

Start by locating the request `Builder` API and reviewing how it currently constructs URLs. Compare the query-value helpers in reqwest and ureq, then determine how conditional values should be URL-encoded and appended; done means the Builder supports this without manual URL concatenation and the behavior is documented and covered by the project’s existing checks.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.