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/title.rs

@@ -14,7 +14,7 @@ fn app() -> Element {
         div {
             // You can set the title of the page with the Title component
             // In web applications, this sets the title in the head. On desktop, it sets the window title
-            Title { "My Application (Count {count})" }
+            document::Title { "My Application (Count {count})" }
             button { onclick: move |_| count += 1, "Up high!" }
             button { onclick: move |_| count -= 1, "Down low!" }
         }