Deploy action should deploy to both the release folder *and* dev on release

[jni]

I just had a minor heart attack thinking that the docs deployment had failed for 0.5.3 because the release notes didn't appear in napari.org/dev. What had actually happened though, is that the release docs had been pushed to napari.org/0.5.3 but not dev. (The previous build to dev had been cancelled by the release build.) Therefore, dev was actually behind stable, which would be fixed soon enough but is a weird state to be in.

I think this would be most easily solved by making two copies.