Updated to be typescript compatable

[Lee-Ashmore]

Migrate Gilded Rose to TypeScript + Add Mocha Test Suite

Summary

This PR converts the Gilded Rose repository from JavaScript to TypeScript and introduces a Mocha/Chai test suite with a custom assertion plugin.

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Changes

TypeScript Migration

• Renamed all .js source files to .ts
• Added strict TypeScript configuration via tsconfig.json
• Added @types/node, typescript, and ts-node/tsx as dev dependencies
• Updated package.json main entry and build script to reflect .ts source and compiled .js output in dist/

Test Infrastructure

• Installed and configured Mocha as the test runner with Chai as the assertion library
• Added .mocharc.json to configure tsx as the TypeScript loader, test file glob, and setup file loading
• Added test and test:watch scripts to package.json

Custom Chai Plugin

• Created src/test/plugins/inventory-check.ts — a reusable Chai plugin exposing the toMatchSellInAndQuality(sellIn, quality) assertion for validating item state after a tick()
• Created src/test/setup.ts — registers the plugin globally via chai.use() so all test files get the assertion automatically
• Added TypeScript type augmentation (declare global) so the custom method typechecks correctly across the project

Test Coverage

• Added src/gilded-rose.test.ts covering all current item types:
  • Normal Item
  • Aged Brie
  • Sulfuras (Legendary)
  • Backstage Passes
• Conjured Item tests are present but skipped (describe.skip) pending implementation

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How to Run

# Run tests once
npm test

# Run in watch mode during development
npm run test:watch

# Build TypeScript
npm run build