docs: update README.md

Author: allcontributors[bot]

README.md

@@ -274,6 +274,7 @@ Thanks goes to these people ([emoji key][emojis]):
     <td align="center"><a href="http://www.joshuakgoldberg.com"><img src="https://avatars1.githubusercontent.com/u/3335181?v=4" width="100px;" alt=""/><br /><sub><b>Josh Goldberg</b></sub></a><br /><a href="https://github.com/testing-library/dom-testing-library/commits?author=JoshuaKGoldberg" title="Code">💻</a> <a href="https://github.com/testing-library/dom-testing-library/commits?author=JoshuaKGoldberg" title="Tests">⚠️</a></td>
     <td align="center"><a href="http://kengregory.com"><img src="https://avatars0.githubusercontent.com/u/3155127?v=4" width="100px;" alt=""/><br /><sub><b>Ken Gregory</b></sub></a><br /><a href="https://github.com/testing-library/dom-testing-library/commits?author=kgregory" title="Code">💻</a> <a href="https://github.com/testing-library/dom-testing-library/commits?author=kgregory" title="Tests">⚠️</a></td>
     <td align="center"><a href="https://www.jacobparis.com/"><img src="https://avatars2.githubusercontent.com/u/5633704?v=4" width="100px;" alt=""/><br /><sub><b>Jacob Paris</b></sub></a><br /><a href="https://github.com/testing-library/dom-testing-library/commits?author=JacobParis" title="Code">💻</a> <a href="https://github.com/testing-library/dom-testing-library/commits?author=JacobParis" title="Tests">⚠️</a></td>
+    <td align="center"><a href="https://keiya01.github.io/portfolio"><img src="https://avatars1.githubusercontent.com/u/34934510?v=4" width="100px;" alt=""/><br /><sub><b>keiya sasaki</b></sub></a><br /><a href="https://github.com/testing-library/dom-testing-library/commits?author=keiya01" title="Documentation">📖</a></td>
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