Add the simple builder as the default example

Author: sunsided

README.md

@@ -13,7 +13,7 @@ The initial `?` question mark is automatically prepended.
 use query_string_builder::QueryString;
 
 fn main() {
-    let qs = QueryString::new()
+    let qs = QueryString::simple()
         .with_value("q", "apple")
         .with_value("tasty", true)
         .with_value("weight", 70.0)

src/lib.rs

@@ -8,7 +8,7 @@
 //! ```
 //! use query_string_builder::QueryString;
 //!
-//! let qs = QueryString::dynamic()
+//! let qs = QueryString::simple()
 //!             .with_value("q", "🍎 apple")
 //!             .with_value("tasty", true)
 //!             .with_opt_value("color", None::<String>)