- consider `juniper_graphql_transport_ws` crate on CI
- implement auto-selection of protocol in `juniper_warp` crate
- support `graphql-transport-ws` protocol in `juniper_actix` crate
- implement auto-selection of protocol in `juniper_actix` crate
Additionally:
- move `examples/warp_subscriptions` into `juniper_warp/examples/subscription.rs`
- move `examples/actix_subscriptions` into `juniper_actix/examples/subscription.rs`
- move `examples/basic_subscriptions` into `juniper_subscriptions/examples/basic.rs`
- bump up MSRV of `juniper_actix` crate to 1.68
