Add an ability to use 'isRevealingMask' option

[IIaJIeHo]

I've added an ability to use isRevealingMask with this component. The description for this option is in https://github.com/insin/inputmask-core#isrevealingmask--boolean

[andersryanc]

+1

I noticed this option today while reading over the inputmask-core docs and would love to have this integrated!

Specifically, I think it's annoying when the input is masked with and underscore ("_") or space (" ") and you have to delete back through all that to enter in more text. And when you set the placeholderChar prop to false or an empty string '' it just defaults back to the underscore.

[reddo]

+1 for this prop. I would also like to see this implemented.