update changelog

Author: benvanwerkhoven

CHANGELOG.md

@@ -3,6 +3,9 @@ All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [1.0.0] - Unreleased
+- HIP backend to support tuning HIP kernels on AMD GPUs
+- Experimental features for mixed-precision and accuracy tuning
+- Experimental features for OpenACC tuning
 - Major speedup due to new parser and using revamped python-constraint for searchspace building
 - Implemented ability to use `PySMT` and `ATF` for searchspace building
 - Added Poetry for dependency and build management