switch to a Document trait and introduce Script/Head/Style/Meta components (#2635)

* switch to a Document trait and introduce Script/Head/Style/Meta components

* Fix desktop title

* Insert special elements into the head during the inital SSR render

* Make all head component attributes optional

* hydrate head elements

* improve the server streaming head warning

* Document fullstack head hydration approach

* deduplicate head elements by href

* move Link into head::Link

* document head components

* add meta and title examples

* Fix a few doc examples

* fix formatting

* Add title to playwright tests

* serde is optional on web, but it is enabled by hydrate

* remove leftover console log

packages/fullstack/src/lib.rs

@@ -18,6 +18,8 @@ pub mod launch;
 
 pub use config::*;
 
+#[cfg(feature = "document")]
+mod document;
 #[cfg(feature = "server")]
 mod render;
 #[cfg(feature = "server")]