Add codec README

protocols/v2/codec-sv2/README.md

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+# `codec_sv2`
+
+[![crates.io](https://img.shields.io/crates/v/codec_sv2.svg)](https://crates.io/crates/codec_sv2)
+[![docs.rs](https://docs.rs/codec_sv2/badge.svg)](https://docs.rs/codec_sv2)
+[![rustc+](https://img.shields.io/badge/rustc-1.75.0%2B-lightgrey.svg)](https://blog.rust-lang.org/2023/12/28/Rust-1.75.0.html)
+[![license](https://img.shields.io/badge/license-MIT%2FApache--2.0-blue.svg)](https://github.com/stratum-mining/stratum/blob/main/LICENSE.md)
+[![codecov](https://codecov.io/gh/stratum-mining/stratum/branch/main/graph/badge.svg?flag=codec_sv2-coverage)](https://codecov.io/gh/stratum-mining/stratum)
+
+`codec_sv2` provides the message encoding and decoding functionality for the Stratum V2 (Sv2)
+protocol, handling secure communication between Sv2 roles. This crate abstracts the complexity of
+message encoding/decoding with optional Noise protocol support, ensuring both regular and encrypted
+messages can be serialized, transmitted, and decoded consistently and reliably.
+
+## Main Components
+
+- **Encoder**: Encodes Sv2 messages with or without Noise protocol support.
+- **Decoder**: Decodes Sv2 messages with or without Noise protocol support.
+- **Handshake State**: Manages the current Noise protocol handshake state of the codec.
+
+
+## Usage
+
+To include this crate in your project, run:
+
+```bash
+cargo add codec_sv2
+```
+
+This crate can be built with the following feature flags:
+
+- `noise_sv2`: Enables support for Noise protocol encryption and decryption.
+- `with_buffer_pool`: Enables buffer pooling for more efficient memory management.
+- `with_serde`: builds [`binary_sv2`](https://crates.io/crates/binary_sv2) and
+  [`buffer_sv2`](https://crates.io/crates/buffer_sv2) crates with `serde`-based encoding and
+  decoding. Note that this feature flag is only used for the Message Generator, and deprecated
+  for any other kind of usage. It will likely be fully deprecated in the future.
+
+### Examples
+
+This crate provides two examples demonstrating how to encode and decode Sv2 frames:
+
+1. **[Unencrypted Example](https://github.com/stratum-mining/stratum/blob/main/protocols/v2/codec-sv2/examples/unencrypted.rs)**:
+   Encode and decode standard Sv2 frames, detailing the message serialization and transmission
+   process for unencrypted communications.
+
+2. **[Encrypted Example](https://github.com/stratum-mining/stratum/blob/main/protocols/v2/codec-sv2/examples/encrypted.rs)**:
+   Encode and decode Sv2 frames with Noise protocol encryption, detailing the entire encryption
+   handshake and transport phase and serialization and transmission process for encrypted
+   communications.