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>

packages/dioxus-lib/src/lib.rs

@@ -16,6 +16,9 @@ pub mod events {
 #[cfg(feature = "html")]
 pub use dioxus_html as html;
 
+#[cfg(feature = "html")]
+pub use dioxus_document as document;
+
 #[cfg(feature = "macro")]
 pub use dioxus_rsx as rsx;