chose: use keep a changelog format

Author: codeadict

CHANGELOG.md

@@ -1,16 +1,43 @@
 # Changelog
 
-## 0.1.0
+All notable changes to this project will be documented in this file.
+
+## 0.1.0 (2025-03-18)
 
 Initial release.
 
-- HTTP/1.1 and HTTP/2 client support
-- Unified API across both protocols via `gen_http` module
-- ALPN protocol negotiation for HTTPS
-- Active and passive socket modes
-- Request pipelining (HTTP/1.1) and stream multiplexing (HTTP/2)
-- HPACK header compression with Huffman coding
-- Flow control (HTTP/2)
-- Structured error types with retry classification
-- Connection metadata via private key-value store
-- TLS certificate verification enabled by default
+### Added
+
+- **Unified API** - `gen_http` module works with both HTTP/1.1 and HTTP/2
+  connections through a single interface. Protocol selection is automatic
+  via ALPN for HTTPS, HTTP/1.1 for plain HTTP.
+
+- **HTTP/1.1 state machine** (`gen_http_h1`) - Request pipelining, keep-alive,
+  chunked transfer encoding, body streaming for requests and responses.
+
+- **HTTP/2 state machine** (`gen_http_h2`) - Stream multiplexing, connection
+  and stream level flow control, settings negotiation, GOAWAY handling,
+  server push support. RFC 9113 compliant.
+
+- **HPACK header compression** (`gen_http_parser_hpack`) - Static and dynamic
+  tables with Huffman coding. Pure data structure, no process state.
+  RFC 7541 compliant.
+
+- **Active and passive socket modes** - Active mode delivers data as Erlang
+  messages via `stream/2`. Passive mode uses blocking `recv/3`. Switch
+  between them at any time with `set_mode/2`.
+
+- **Structured error types** - Errors are tagged as `{transport_error, _}`,
+  `{protocol_error, _}`, or `{application_error, _}`. Use
+  `is_retriable_error/1` to decide whether to retry.
+
+- **Connection metadata** - `put_private/3`, `get_private/2,3`,
+  `delete_private/2` for attaching pool IDs, metrics, or tags to
+  connections.
+
+- **Transport abstraction** - `gen_http_transport` behaviour with TCP
+  (`gen_http_tcp`) and SSL/TLS (`gen_http_ssl`) implementations.
+  TLS certificate verification enabled by default.
+
+- **Zero dependencies** - Only OTP stdlib (kernel, stdlib, crypto,
+  public_key, ssl). Targets OTP 25+.