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/image_generator_openai.rs

@@ -36,7 +36,7 @@ fn app() -> Element {
     });
 
     rsx! {
-        head::Link { rel: "stylesheet", href: "https://unpkg.com/bulma@0.9.0/css/bulma.min.css" }
+        document::Link { rel: "stylesheet", href: "https://unpkg.com/bulma@0.9.0/css/bulma.min.css" }
         div { class: "container",
             div { class: "columns",
                 div { class: "column",