Add ContextHandle in yew::prelude (#2372)

* Adds ContextHandle in yew::prelude

* Adds ContextHandle in yew::prelude

Added ContextHandle in /yew/src/lib.rs and updated stderr with test-overwrite

* Formats code using cargo fmt

* Revert "Adds ContextHandle in yew::prelude"

This reverts commit abdf21f.

Author: lameferret

packages/yew/src/lib.rs

@@ -376,7 +376,7 @@ where
 pub mod prelude {
     pub use crate::app_handle::AppHandle;
     pub use crate::callback::Callback;
-    pub use crate::context::ContextProvider;
+    pub use crate::context::{ContextHandle, ContextProvider};
     pub use crate::events::*;
     pub use crate::html::{
         create_portal, BaseComponent, Children, ChildrenWithProps, Classes, Component, Context,