Update CONTRIBUTORS.md and CHANGELOG.md

Author: andrehora

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Changed
+
+- Updated test_cells to cover boundary cases of cell_len
+
 ## [13.3.1] - 2023-01-28
 
 ### Fixed

CONTRIBUTORS.md

@@ -17,6 +17,7 @@ The following people have contributed to the development of Rich:
 - [Michał Górny](https://github.com/mgorny)
 - [Nok Lam Chan](https://github.com/noklam)
 - [Leron Gray](https://github.com/daddycocoaman)
+- [Andre Hora](https://github.com/andrehora)
 - [Kenneth Hoste](https://github.com/boegel)
 - [Lanqing Huang](https://github.com/lqhuang)
 - [Finn Hughes](https://github.com/finnhughes)