Referenced a Fiber architecture explanation (#1448)

Added a link to an article that provides an in-depth explanation of Fiber architecture.

Author: maxkoretskyi

content/docs/codebase-overview.md

@@ -211,7 +211,7 @@ Its main goals are:
 * Ability to return multiple elements from `render()`.
 * Better support for error boundaries.
 
-You can read more about it in [React Fiber Architecture](https://github.com/acdlite/react-fiber-architecture). While it has shipped with React 16, the async features are not enabled by default yet.
+You can read more about React Fiber Architecture [here](https://github.com/acdlite/react-fiber-architecture) and [here](https://blog.ag-grid.com/index.php/2018/11/29/inside-fiber-in-depth-overview-of-the-new-reconciliation-algorithm-in-react). While it has shipped with React 16, the async features are not enabled by default yet.
 
 Its source code is located in [`packages/react-reconciler`](https://github.com/facebook/react/tree/master/packages/react-reconciler).