Added a drop shadow to the `ColorPickerModal` to increase contrast between the modal and the background.
Talked to @atul about this -- but the shadow is noticeably jagged/not smooth around the edge of the modal. New to React Native, so I'm open to approaches about how to fix this:
- (Current approach) Continue using Shadow Props, but fine-tuning the actual values (height, width, or the `shadowRadius`) to make the shadow smoother
- Not using a drop shadow, but a stroke or something similar instead
- Another styling approach