Add ExtendsClass to 在线工具 / 在线资源.md

Author: cyr1l0u

Cross-Platform/Javascript/在线资源.md

@@ -12,6 +12,7 @@
 - [Home - SmallDev.tools](https://smalldev.tools/) -- 在线开发工具
 - [Carbon | Create and share beautiful images of your source code](https://carbon.now.sh/) -- 输入代码生成高亮的对应代码格式图片
 - [Can I use... Support tables for HTML5, CSS3, etc](https://caniuse.com/) -- 代码版本兼容性检查
+- [ExtendsClass](https://extendsclass.com/) -- 在线开发工具
 - [Regex Vis (regex-vis.com)](https://regex-vis.com/) -- 在线生成正则表达式
 - [RunJS - JavaScript Playground](https://runjs.app/) -- JS在线编辑器
 - [Unminify JS, CSS, HTML, XML and JSON Code](https://unminify.com/) -- 代码格式化工具
@@ -81,4 +82,4 @@
 - [ColorDrop](https://colordrop.io/)
 - [Coolors - The super fast color palettes generator!](https://coolors.co/)
 - [BrandColors - official brand color hex codes](https://brandcolors.net/)
-- [LOL Colors - Curated color palette inspiration (webdesignrankings.com)](https://www.webdesignrankings.com/resources/lolcolors/)
+- [LOL Colors - Curated color palette inspiration (webdesignrankings.com)](https://www.webdesignrankings.com/resources/lolcolors/)