docs: update

Author: hyrious

docs/en/faq.md

@@ -13,6 +13,20 @@ This means that your bundler does not handle CJS-ESM interop well, see
 
 Please try another bundler like [esbuild](https://esbuild.github.io/) or [vite](https://vitejs.dev/).
 
+### \[WindowManger\]: room must be switched to be writable
+
+Fastboard requires at least one `writer` user to initialize the states.
+If the first user is not a `writer`, then the error will occur on the joinning room.
+It is recommended to give all users `writer` tokens no matter what their initial permissions should be.
+
+By giving all users `writer` tokens, it is also convenient to implement things like
+switching whiteboard permissions. It only needs relevant users to call the API:
+
+```js
+// disallow current user to operate the whiteboard
+fastboard.room.setWritable(false);
+```
+
 ### How to customize the toolbar's apps panel
 
 You can use the `apps` variable to do so, see

docs/zh/faq.md

@@ -7,6 +7,10 @@
 > [!NOTE]
 > 这个错误在 0.3.8 后已经被修复了，请检查你的依赖版本。
 
+### \[WindowManger\]: room must be switched to be writable
+
+Fastboard 需要至少一个有 `writer` 权限的用户进入房间来初始化数据，如果第一位用户没有这个权限就会报错。这里推荐给所有用户 (无论是你业务里的老师、学生、助教) 发放 `writer` 权限的 room token。同时，这种做法也有利于实现例如白板权限切换等业务，只需要相关用户调用 `fastboard.room.setWritable(true / false)` 即可。
+
 ### 如何使用代码操作 App
 
 不支持。或者说这部分交互完全由 App 本身定义，Fastboard (Window Manager) 只是提供了一些基建让他们实现同步。内置的那些 App（包括 PPT/PDF 文档查看器、音视频播放器、代码编辑器、倒计时、GeoGebra 等）均不支持任何外部操作。