Please, add `contentContainerStyle` gap style support

Problem Statement

Can we have a way to adjust the spacing between items? At the moment, contentContainerStyle allows us to only adjust the padding and background color.

Proposed Solution

It would be helpful to have the ability to customize the layout in the recycler code.

Example Usage

<FlashList gap={20} />

Alternatives Considered

I can create some invisible gaps between items using ItemSeparatorComponent={renderGap}, or I can adjust the margins of each item.

Priority

• Critical - Blocking my project
• High - Significant improvement to my workflow
• Medium - Would be nice to have
• Low - Minor enhancement

Additional Context

Currently, this breaks the promise of a "drop-in replacement for FlatList", as FlashList does not support all the styling options available in React Native.

By the way, the TS misleads users by resolving styles as a full set of styles. Without referring to the documentation, it is difficult to determine what is going wrong and why.

Checklist

• I've searched existing issues and discussions
• I've provided clear use cases for this feature
• I'm willing to help test this feature if implemented

Start by tracing how FlashList handles contentContainerStyle and how the recycler code lays out items. Compare the requested gap behavior with the existing ItemSeparatorComponent workaround and the proposed API. Done means spacing can be configured as requested, existing padding and background styling still work, and the supported TypeScript styling surface is accurate.