fix: enhance type definitions

[damonbauer]

• Adds SectionData generic to getItemLayout function
• Exports a type for the getItemLayout function
• Additional small cleanup of arguments

Closes #110 (thanks, @andrejpavlovic)

[Copilot]

Pull Request Overview

This PR enhances type definitions for the getItemLayout function by adding generic support for section data types and improving type safety. The changes address issue #110 by providing better TypeScript support and making the function more flexible for different data structures.

• Adds generic SectionT parameter to support custom section data types
• Exports a new GetItemLayoutFunction type for better type inference
• Updates parameter names for consistency and improves null checking logic

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[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	100%	77 / 77
🔵	Statements	100%	77 / 77
🔵	Functions	100%	2 / 2
🔵	Branches	100%	19 / 19

File Coverage

File	Stmts	Branches	Functions	Lines	Uncovered Lines
Changed Files
src/index.ts	100%	100%	100%	100%

Generated in workflow #279 for commit 09ac0a5 by the Vitest Coverage Report Action