Add note re: viseme/eyelook shapekeys not being syncable

docs/docs/reference/blendshape-sync.md

@@ -20,6 +20,8 @@ Blendshape Sync always copies the same value from one renderer's blendshape to a
 
 Blendshape Sync cannot be chained - that is, you can copy from A to B and A to C, but you can't copy from A to B and B to C.
 
+At runtime, Blendshape Sync only supports syncing blendshapes that are controlled by animators. Blendshapes controlled by VRChat's builtin eyelook or viseme systems cannot be synced accurately. 
+
 ## Setting up Blendshape Sync
 
 Add the Blendshape Sync component to an object in your prefab. Then click the + button to open a selection window.

docs/i18n/ja/docusaurus-plugin-content-docs/current/reference/blendshape-sync.md

@@ -21,6 +21,10 @@ Blendshape Syncは一つのレンダラーのBlendshapeを別のレンダラー
 
 Blendshape Syncは連鎖的に使うことができません。A→BとA→Cなら大丈夫ですが、A→BとB→Cは正しく動作しません。
 
+At runtime, Blendshape Sync only supports syncing blendshapes that are controlled by animators. Blendshapes controlled by VRChat's builtin eyelook or viseme systems cannot be synced accurately.
+
+プレイ中は、Blendshape Syncはアニメーターにより制御されるブレンドシェープのみを同期できます。VRChat内包の目線・口パクシステムで直接操作されるブレンドシェープが正しく同期されませんので注意。
+
 ## 設定方法
 
 レンダラー付きオブジェクトにBlendshape Syncを追加してください。そして、+ボタンを押して選択ウィンドウを開きます。