Implement ` juniper_graphql_ws::Schema` for `&'static RootNode`

[JonahPlusPlus]

Is your feature request related to a problem? Please describe.
Currently, the Schema trait is only implemented for Arc<RootNode>. Arc creates overhead that can be avoided for permanent resources.

Describe the solution you'd like
Implement Schema for &'static RootNode or for types that implement Deref<Target = RootNode> (or could Schema just be replaced with Deref?).
Then, users can create a static reference via Box::leak.

Describe alternatives you've considered
Right now, I'm just using a newtype to implement Schema. It works, but feels like boilerplate.