[FEATURE]Apply theme onload

[LiuZiHua-Andrew]

Is your feature request related to a problem? Please describe.
Currently I wanted to render pbi report with custom theme, whereas I can use after load to customize them on going but it will have a flip between original theme and new theme

Describe the solution you'd like
I checked that we only allowed predefined props being embeded as config, can we add the new feature theme in or you can have a ...extraProps similar to your ...extraSettings so that there is no need to keep updating the new features

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.