"Viewer 1" updates/requests fail once "Viewer 2" is created

When there are multiple viewers within one notebook only calls to the most recently created viewer succeed. For example:
```
viewer_1 = view(image)
```
```
viewer.set_rotate(True) # succeeds
```
```
viewer_2 = view(image)
```
```
viewer.set_rotate(False) # fails
viewer_2.set_rotate(True) # succeeds
```

Originally this seemed to be related to the major updates now available in `v1.0a41` - For example, the cells
```
annotations = viewer.get_annotations_enabled
```
```
annotations
```
return
```
TypeError: Cannot read properties of undefined (reading 'getAnnotationsEnabled')
```
Testing with previous releases shows that this is actually a long-standing issue. It seems that the reference to the window object returned from `api.createWindow` no longer has the [ImJoyPluginAPI](https://github.com/Kitware/itk-vtk-viewer/blob/master/src/ImJoyPluginAPI.js) available after another window is created.

@oeway Have you seen behavior like this before?