update CHANGELOG

Author: uint

CHANGELOG.md

@@ -8,6 +8,26 @@ and this project adheres to
 
 ## [Unreleased]
 
+### Added
+
+- cosmwasm-std: Add `from_msgpack`, `to_msgpack_vec` and `to_msgpack_binary`.
+  These functions are meant to be used similarly to their JSON counterparts.
+  [MessagePack](https://msgpack.org) is a more compact, binary encoding.
+  ([#2118])
+
+[#2118]: https://github.com/CosmWasm/cosmwasm/pull/2118
+
+### Changed
+
+- cosmwasm-std: `Binary`, `HexBinary` and `Checksum` are now encoded as binary
+  blobs when used together with a "compact" `serde` encoding. A compact encoding
+  is an encoding that returns `false` from
+  [`is_human_readable`](https://docs.rs/serde/latest/serde/trait.Serializer.html#method.is_human_readable).
+  This is to make these types more efficient when used together with the new
+  [MessagePack](https://msgpack.org) encoding. ([#2118])
+
+[#2118]: https://github.com/CosmWasm/cosmwasm/pull/2118
+
 ## [2.1.1] - 2024-07-30
 
 ### Fixed