Update room section of CONTRIBUTING.md

CONTRIBUTING.md

@@ -39,10 +39,12 @@ Misskey uses CircleCI for executing automated tests.
 Configuration files are located in [`/.circleci`](/.circleci).
 
 ## Adding MisskeyRoom items
-* Use English for material, object and texture names
-* Use meter for unit of length
-* Your PR should include all source files of your models (for later editing)
-* Your PR must include the glTF binary files (.glb) of your models
+* Use English for material, object and texture names.
+* Use meter for unit of length.
+* Your PR should include all source files (e.g. `.png`, `.blend`) of your models (for later editing).
+* Your PR must include the glTF binary files (`.glb`) of your models.
+* Add a locale key `room.furnitures.YOUR_ITEM` at [`/locales/ja-JP.yml`](/locales/ja-JP.yml).
+* Add a furniture definition at [`/src/client/app/common/scripts/room/furnitures.json5`](/src/client/app/common/scripts/room/furnitures.json5).
 
 If you have no experience on 3D modeling, we suggest to use the free 3DCG software [Blender](https://www.blender.org/).
 You can find information on glTF 2.0 at [glTF 2.0 — Blender Manual]( https://docs.blender.org/manual/en/dev/addons/io_scene_gltf2.html).