big

This pull request introduces a comprehensive test infrastructure for the Big presentation library, including automated testing, documentation, and supporting files. The main changes are the addition of a GitHub Actions workflow for running tests, a with test scripts and dependencies, a detailed test suite README, and a test HTML fixture. It also adds a status badge to the main to show test results. Testing Infrastructure and Automation: Added a GitHub Actions workflow () to automatically run tests and generate coverage reports on pushes and pull requests for Node.js versions 18.x and 20.x. Created a with scripts for running tests, watching tests, and generating coverage reports, and added necessary dev dependencies (, , , ). Documentation: Added with detailed instructions on running tests, test structure, coverage, dependencies, and notes about integration testing limitations. Updated to include a badge displaying the status of the test workflow. Testing Support Files:** Added , an HTML file that acts as a fixture for integration and DOM-based tests, containing sample slides and elements to exercise presentation features.