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>

packages/static-generation/src/ssg.rs

@@ -1,4 +1,5 @@
 use dioxus_isrg::*;
+use dioxus_lib::document::Document;
 use dioxus_lib::prelude::*;
 use dioxus_router::prelude::*;
 use dioxus_ssr::renderer;