Add missing strictMode prop to FlatList TypeScript types

[drhops]

Summary:

FlatList's strictMode prop is implemented in the component and declared in the Flow types (OptionalFlatListProps in FlatList.js), but missing from the shipped TypeScript definitions. TS users can't set it on without augmenting the module themselves. This adds strictMode?: boolean to the TypeScript FlatListProps, matching the Flow declaration. Types-only, no runtime change.

Changelog:

[GENERAL] [ADDED] - Add missing strictMode prop to FlatList TypeScript types

Test Plan:

Types-only change:

• Before, <FlatList ... strictMode /> errored (Property 'strictMode' does not exist);
• After, it type-checks. Matches the Flow prop and the runtime use in render(): const renderer = strictMode ? this._memoizedRenderer : this._renderer;

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[meta-codesync]

@Abbondanzo has imported this pull request. If you are a Meta employee, you can view this in D113631325.