Adding minimal documentation

Author: lemire

README.md

@@ -2,3 +2,25 @@
 
 Fast [WHATWG specification](https://url.spec.whatwg.org) compliant URL parser for Rust.
 
+### Usage
+
+Add the following as a dependency to your project (`Cargo.toml`):
+
+```
+[dependencies]
+ada-url = { git = "https://github.com/ada-url/rust" }
+```
+
+Here is an example illustrating a common usage:
+```Rust
+use ada_url::Url;
+fn main() {
+    let mut u = Url::parse("http://www.google:8080/love#drug", None).expect("bad url");
+    println!("port: {:?}", u.port());
+    println!("hash: {:?}", u.hash());
+    println!("pathname: {:?}", u.pathname());
+    println!("href: {:?}", u.href());
+    u.set_port("9999");
+    println!("href: {:?}", u.href());
+}
+```