docs: fix a broken link (#1448)

Author: asifm

packages/docs/docs/miscellaneous/design-concepts.md

@@ -16,7 +16,7 @@ VuePress 1.0 has been rewritten extensively, and the most important one is the i
 
 ### Decoupling
 
-With plugins, we can implement many of the core functions with plugins, and you can see many built-in plugins [here](https://github.com/vuejs/vuepress/tree/master/packages/%40vuepress/core/lib/internal-plugins) that cover many of the core functions of VuePress, which used to blend in all parts of the code base, but now they're clear at a glance.
+With plugins, we can implement many of the core functions with plugins, and you can see many built-in plugins [here](https://github.com/vuejs/vuepress/tree/master/packages/%40vuepress/core/lib/node/internal-plugins) that cover many of the core functions of VuePress, which used to blend in all parts of the code base, but now they're clear at a glance.
 
 ### Configuration management