[Enhancement] Row expansion indication

[mikkurogue]

Is your feature request related to a problem? Please describe.
When using the rowExpansion props, it is not always clear that a row can be expanded (or is clickable for expansion etc).

Describe the solution you'd like
A new prop added to the rowExpansion methods to allow for an indicator (i.e. chevron right for closed and chevron down for expanded/open). Icons should be provided by the user, as not everyone uses the same icon libraries so this would be deemed as required props when rowExpansion.indicators = true for instance.

Describe alternatives you've considered
A pseudo column that calculates which row(s) are expanded already. See this gist: https://gist.github.com/mikkurogue/b5add794faa2933e2a644959ca77524b

Additional context
N/A