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

examples/dynamic_asset.rs

@@ -24,7 +24,7 @@ fn app() -> Element {
     });
 
     rsx! {
-        head::Link { rel: "stylesheet", href: STYLE }
+        document::Link { rel: "stylesheet", href: STYLE }
         h1 { "Dynamic Assets" }
         img { src: "/logos/logo.png" }
     }