⚠️ Is your feature request related to a problem? Please describe

Currently there is some inconsistency in having README in develop branch.
In case of adding some feature and its description into develop users see this description and think that this feature is available in the latest stable release, while it might be not released yet. Such situation happened recently.
Also, Chuc

Currently websockets are unsupported:

class SttpBackendStub[F[_], S] private (
    monad: MonadError[F],
    matchers: PartialFunction[Request[_, _], F[Response[_]]],
    fallback: Option[SttpBackend[F, S, NothingT]]
) extends SttpBackend[F, S, NothingT] { // TODO

(note the TODO for the NothingT type parameter which specifies what kind of websockets are supported).

The bac