A query string builder for percent encoding key-value pairs

This is a tiny helper crate for simplifying the construction of URL query strings. The initial ? question mark is automatically prepended.

Example

```rust use querystringbuilder::QueryString;

fn main() { let qs = QueryString::new() .withvalue("q", "apple") .withoptvalue("color", None::) .withopt_value("category", Some("fruits and vegetables?"));

assert_eq!(
    format!("https://example.com/{qs}"),
    "https://example.com/?q=apple&category=fruits%20and%20vegetables?"
);

} ```