Add comprehensive unit tests and CI workflow

[naheel0]

Title: Add comprehensive unit tests and CI workflow

Problem

The repository lacks automated tests and CI; changes are risky and regressions may slip into master.

Proposed change

Add unit tests for core functionality (matcher, formatter, i18n, CLI) and a GitHub Actions workflow to run tests on PRs.

Files to add/change

• test/matcher.test.js
• test/formatter.test.js
• test/cli.test.js
• update package.json scripts (test) if needed
• add .github/workflows/test.yml

Tasks

• Pick a test runner (Node built-in node:test or jest) and add dev-dependency if needed.
• Write unit tests for exact/fuzzy match, locale loading, CLI JSON output.
• Add a CI workflow to run npm ci and npm test on PRs.

Acceptance criteria

• Tests run locally via npm test and on GitHub Actions.
• PRs block if tests fail.

Labels: test, ci, high-priority