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>

example-projects/ecommerce-site/src/components/loading.rs

@@ -3,7 +3,7 @@ use dioxus::prelude::*;
 #[component]
 pub(crate) fn ChildrenOrLoading(children: Element) -> Element {
     rsx! {
-        head::Link {
+        document::Link {
             rel: "stylesheet",
             href: asset!("./public/loading.css")
         }