Update README.md

Author: CarGuo

README.md

@@ -28,6 +28,7 @@
 * ### [Flutter 完整开发实战详解(三、打包填坑篇)](https://juejin.im/entry/5b6fd5ee6fb9a009d36a4104 )
 * ### [Flutter 完整开发实战详解(四、Redux、主题、国际化)](https://juejin.im/post/5b79767ff265da435450a873 )
 * ### [Flutter 完整开发实战详解(五、深入探索)](https://juejin.im/post/5bc450dff265da0a951f032b )
+* ### [Flutter完整开发实战详解(六、 深入Widget原理)](https://juejin.im/post/5c7e853151882549664b0543 )