Update list of contributors

Author: stephane-caron

CITATION.cff

@@ -35,3 +35,5 @@ authors:
 - family-names: "Castro"
   given-names: "Sebastian"
   orcid: "https://orcid.org/0000-0001-5754-9959"
+- family-names: "Tao"
+  given-names: "Haixuan Xavier"

README.md

@@ -323,7 +323,7 @@ If you use this project in your works, please cite as follows:
 ```bibtex
 @software{robot_descriptions_py,
   title = {{robot_descriptions.py: Robot descriptions in Python}},
-  author = {Caron, Stéphane and Romualdi, Giulio and Kozlov, Lev and Ordoñez Apraez, Daniel Felipe and Tadashi Kussaba, Hugo and Bang, Seung Hyeon and Zakka, Kevin and Schramm, Fabian and Uru\c{c}, Jafar and Traversaro, Silvio and Castro, Sebastian},
+  author = {Caron, Stéphane and Romualdi, Giulio and Kozlov, Lev and Ordoñez Apraez, Daniel Felipe and Tadashi Kussaba, Hugo and Bang, Seung Hyeon and Zakka, Kevin and Schramm, Fabian and Uru\c{c}, Jafar and Traversaro, Silvio and Castro, Sebastian and Tao, Haixuan Xavier},
   license = {Apache-2.0},
   url = {https://github.com/robot-descriptions/robot_descriptions.py},
   version = {1.18.0},