Convert Project to TypeScript

Overview

This Pull Request aims to convert the existing JavaScript project to TypeScript. The migration to TypeScript enhances code maintainability, provides better type safety, and improves developer experience with modern tooling and autocompletion.

Related Issue

This PR addresses issue #77.

Changes Made

Installed TypeScript: Added TypeScript as a development dependency.
Added tsconfig.json: Created a TypeScript configuration file to manage compiler options.
Renamed Files: Converted .js files to .ts for proper TypeScript support.
Type Annotations: Implemented type annotations throughout the codebase to leverage TypeScript's type system.
Updated Jest Configuration: Configured Jest to work with TypeScript by adding ts-jest preset and ensuring compatibility with TypeScript files.
Refactored Tests: Updated test files to reflect the TypeScript conversion and added type safety to test cases.

Steps Taken

Running the application again with both valid and invalid GTIN numbers.
Running the tests and all tests passed.

Benefits

Improved Type Safety: Reduces the likelihood of runtime errors through static type checking.

@0xflotus Please review the PR and let me know if any further changes are needed

0xflotus / valid-gtin

Convert this project to TypeScript #77 #85