Add a note about release support.

# rust-openssl

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[![crates.io](https://img.shields.io/crates/v/openssl.svg)](https://crates.io/crates/openssl)

OpenSSL bindings for the Rust programming language.

[Documentation](https://docs.rs/openssl).

## Release Support

The current supported release is 0.10.

New major versions will be published at most once per year. After a new

release, the previous major version will be partially supported with bug

fixes for 3 months, after which support will be dropped entirely.

### Contribution

Unless you explicitly state otherwise, any contribution intentionally