Add release notes for 0.24.0.
--------------------------------------------------------------------------------
+## 0.24.0
+
+### Added
+
+* Implement support for `async` functions in Wasmtime
+ [#2434](https://github.com/bytecodealliance/wasmtime/pull/2434)
+
+### Fixed
+
+* Fix preservation of the sigaltstack on macOS
+ [#2676](https://github.com/bytecodealliance/wasmtime/pull/2676)
+* Fix incorrect semver dependencies involving fs-set-times.
+ [#2705](https://github.com/bytecodealliance/wasmtime/pull/2705)
+* Fix some `i128` shift-related bugs in x64 backend.
+ [#2682](https://github.com/bytecodealliance/wasmtime/pull/2682)
+* Fix incomplete trap metadata due to multiple traps at one address
+ [#2685](https://github.com/bytecodealliance/wasmtime/pull/2685)
+
## 0.23.0
Released 2021-02-16.
