add backdrop to date picker component for improved UX on render

[sudomann]

🚀 Feature Proposal

How about adding something like a backdropColor prop to datepicker component?
_{^{This issue was copied from #657 (comment)}}

Motivation

Currently, the calendar that pops up does not do very well to focus the user's attention on it as it renders on the same level/layer as the input component the user tapped on.

In my opinion, it is bad UX to render something that large without distinguishing/emphasizing its separation from the layer of content behind it.

Example

BAD

vs

GOOD

It needs to be made clear that the rendered calendar is in the foreground expecting the user's input and not a part of the page on which they tapped the datepicker.