Spread/pass props on custom placeholders

[burkeshartsis]

When writing custom placeholders I would like my custom placeholder to have access to the props passed ReactPlaceholder. There are a number of ways you could make this intuitive but the easiest way would just be to pass down the ...rest here. An example usage would be... I have a custom placeholder and I want to pass an aria accessibility role as a prop on ReactPlaceholder like role={'progressbar'}.