Move the document trait into a separate crate (#3035)

* add a default head method through eval
* remove the old document trait
* implement document for each platform
* pull out document into a dedicated crate to cut down on shared dependencies
---------

Co-authored-by: Jonathan Kelley <jkelleyrtp@gmail.com>

examples/eval.rs

@@ -19,7 +19,7 @@ fn app() -> Element {
         // The `eval` is available in the prelude - and simply takes a block of JS.
         // Dioxus' eval is interesting since it allows sending messages to and from the JS code using the `await dioxus.recv()`
         // builtin function. This allows you to create a two-way communication channel between Rust and JS.
-        let mut eval = eval(
+        let mut eval = document::eval(
             r#"
                 dioxus.send("Hi from JS!");
                 let msg = await dioxus.recv();
@@ -29,10 +29,10 @@ fn app() -> Element {
         );
 
         // Send a message to the JS code.
-        eval.send("Hi from Rust!".into()).unwrap();
+        eval.send("Hi from Rust!").unwrap();
 
         // Our line on the JS side will log the message and then return "hello world".
-        let res = eval.recv().await.unwrap();
+        let res: String = eval.recv().await.unwrap();
 
         // This will print "Hi from JS!" and "Hi from Rust!".
         println!("{:?}", eval.await);