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/desktop/src/document.rs

@@ -1,4 +1,4 @@
-use dioxus_html::document::{Document, EvalError, Evaluator};
+use dioxus_document::{Document, Eval, EvalError, Evaluator};
 use generational_box::{AnyStorage, GenerationalBox, UnsyncStorage};
 
 use crate::{query::Query, DesktopContext};
@@ -18,17 +18,13 @@ impl DesktopDocument {
 }
 
 impl Document for DesktopDocument {
-    fn new_evaluator(&self, js: String) -> GenerationalBox<Box<dyn Evaluator>> {
-        DesktopEvaluator::create(self.desktop_ctx.clone(), js)
+    fn eval(&self, js: String) -> Eval {
+        Eval::new(DesktopEvaluator::create(self.desktop_ctx.clone(), js))
     }
 
     fn set_title(&self, title: String) {
         self.desktop_ctx.window.set_title(&title);
     }
-
-    fn as_any(&self) -> &dyn std::any::Any {
-        self
-    }
 }
 
 /// Represents a desktop-target's JavaScript evaluator.