Mark 'libsignal' branch as frozen.

README.md

@@ -1,23 +1,3 @@
-# boring
+This branch is no longer actively developed; Signal's additions to `boring` live on the `main` branch. However, because past versions of [libsignal][] depended on this branch rather than on specific tags, it has to stay live in order to not break existing external clients. (And, for the curious, we don't want to put any breaking changes on this branch because that would mess up those same clients' use of `cargo update`.)
 
-[![crates.io](https://img.shields.io/crates/v/boring.svg)](https://crates.io/crates/boring)
-
-BoringSSL bindings for the Rust programming language and TLS adapters for [tokio](https://github.com/tokio-rs/tokio)
-and [hyper](https://github.com/hyperium/hyper) built on top of it.
-
-## Documentation
- - Boring API: <https://docs.rs/boring>
- - tokio TLS adapters: <https://docs.rs/tokio-boring>
- - hyper HTTPS connector: <https://docs.rs/hyper-boring>
- - FFI bindings: <https://docs.rs/boring-sys>
-
-## Contribution
-
-Unless you explicitly state otherwise, any contribution intentionally
-submitted for inclusion in the work by you, as defined in the Apache-2.0
-license, shall be dual licensed under the terms of both the Apache License,
-Version 2.0 and the MIT license without any additional terms or conditions.
-
-## Accolades
-
-The project is based on a fork of [rust-openssl](https://github.com/sfackler/rust-openssl).
+[libsignal]: https://github.com/signalapp/libsignal/