Add Cyrilex to 工具 in RegExp.md (#106)

Author: cyrilbois

docs/JavaScript/RegExp.md

@@ -401,3 +401,4 @@ console.log(dP2.test("2017-02-29"));
 - [正则表达式在线测试工具](http://regex.zjmainstay.cn/)
 - [Regulex：JavaScript正则表达式展示器](https://jex.im/regulex/)
 - [寻找完美的 URL 验证正则表达式](https://mathiasbynens.be/demo/url-regex)
+- [Online regex tester and visualizer](https://extendsclass.com/regex-tester.html)