update changelog

Author: Mark McCaskey

CHANGELOG.md

@@ -5,6 +5,7 @@ All PRs to the Wasmer repository must add to this file.
 Blocks of changes will separated by version increments.
 
 ## **[Unreleased]**
+- [#343](https://github.com/wasmerio/wasmer/pull/343) Implement preopened files for WASI and fix aligment issue when accessing WASI memory
 - [#355](https://github.com/wasmerio/wasmer/pull/355) Misc changes to `Cargo.toml`s for publishing
 - [#352](https://github.com/wasmerio/wasmer/pull/352) Bump version numbers to 0.3.0
 - [#351](https://github.com/wasmerio/wasmer/pull/351) Add hidden option to specify wasm program name (can be used to improve error messages)