Made onRequestClose a prop. Fixes #18

[mthahzan]

It is ideal if the onRequestClose prop of the modal is exposed as an API instead of hiding it by default from the library itself.

[nysamnang]

@mthahzan There is no need to pass props onRequestClose as a function. Instead, i have made it as a boolean to control whether you want to disable back android or not 07c2078 .

If you want that, please kindly upgrade to the latest version.
Thank for your contribution.

[mthahzan]

Yeah, this addresses the issue I raised.

But the current implementation doesn't have the configurability of giving the user onRequestClose handler. For example, if the user wants to show a confirmation and then close on back press, they can't do that with just closeOnPressBack.

I personally would not do it this way. But it's up to you.

[nysamnang]

Yeah, you said it right. But "confirm to close modal" i think it will never happen 😄.