message: doc: add component location guide
diff: @@ -64,6 +64,40 @@ viewer.dataSources.add(dataSource);
  Such cases are also in other components. For details, refer to "Available scope" in the document of each component.
  +## Component location
  +
  +Please place each component as close as possible under Viewer or CesiumWidget component to avoid extra rendering. Make component hierarchy shallow as possible.
  +
  +Exception are:
  +
  +- `Entity` > `*Graphics`
  +- `Entity` > `EntityDescription`
  +- `ScreenSpaceEventHandler` > `ScreenSpaceEvent`
  +- `xCollection` > `x`
  +- `CustomDataSource` > `Entity`
  +
  +e.g.: `Scene` > `Camera` or `Camera` > `Entity` is not recommended.
  +
  +```jsx
  +// not recomended
  +<Viewer>
  + <Scene>
  + <Camera>
  + <Entity />
  + </Camera>
  + </Scene>
  +</Viewer>
  +```
  +
  +```jsx
  +// recomended
  +<Viewer>
  + <Scene />
  + <Camera />
  + <Entity />
  +</Viewer>
  +```
  +
  ## Properties
  Each components of resium have 4 kinds of properties as bellow.
  