Support passing Emotion 10 css objects in params

**Affected Projects**

React
**Is your feature request related to a problem? Please describe.**

Now that the project is using Emotion 10 css function now returns an object not a class name
however I've been using ReactiveList
with listClass parameter, which takes a string so this doesn't work anymore

The clunky solution I found was to wrap the whole component in `` https://emotion.sh/docs/class-names

Can these parameters internally perhaps handle this so that i can just pass a css` object straight in

Thanks