Document uploads development guidelines

Explain Workhorse acceleration features

doc/development/README.md

@@ -65,6 +65,7 @@ description: 'Learn how to contribute to GitLab.'
 - [Repository mirroring](repository_mirroring.md)
 - [Git LFS](lfs.md)
 - [Developing against interacting components or features](interacting_components.md)
+- [File uploads](uploads.md)
 
 ## Performance guides
 

doc/development/file_storage.md

@@ -2,6 +2,8 @@
 
 We use the [CarrierWave] gem to handle file upload, store and retrieval.
 
+File uploads should be accelerated by workhorse, for details please refer to [uploads development documentation](uploads.md).
+
 There are many places where file uploading is used, according to contexts:
 
 - System