Add changelog entry for tuning of elementwise functions

Author: oleksandr-pavlyk

CHANGELOG.md

@@ -32,6 +32,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * Build translation unit "simplify_iteration_space.cpp" compiled multiple times as a static library [gh-1847](https://github.com/IntelPython/dpctl/pull/1847)
 * Fix warning in documentation generation caused by `diff` docstring [gh-1855](https://github.com/IntelPython/dpctl/pull/1855)
 * Fix additional warnings when generating docs [gh-1861](https://github.com/IntelPython/dpctl/pull/1861)
+* Tuning work for elementwise functions with modest performance gains (under 10%) [gh-1889](https://github.com/IntelPython/dpctl/pull/1889)
 
 ## [0.18.1] - Oct. 11, 2024