Add Jest Framework, JSLint, and Testing Workflow

[PTheocharis]

Description: This pull request focuses on improving testing and code quality.

Changes -New package.json file to add Jest and JSLint

-Added Jest Framework: Implemented Jest using npm. Jest is now configured to run tests located in the "tests" directory.

-Added JSLint as it was suggested as a development dependency.

-Added a GitHub Actions workflow file (js-lint-test.yml) to automate the process of running JSLint and Jest tests. This workflow showcases all the JSLint remarks and the testing results

Added 4 Initial Unit Tests for camelize function and events function (TRIGGER Chapter) in the core.js file. These tests are written using Jest and utilize mocking techniques, because I didn't want to export the extension object and make changes in the core.js

Created a jest.config.js file to improve the process.

Additional Notes: All five tests have been successfully executed, confirming the reliability and effectiveness of the Jest in the core.js file. I tried to keep up good quality standards, I would be happy if yoy help me with any needed improvements as I am still a beginner :)

[ImprovedTube]

thank you!

(didnt review yet.)

---

BTW can we reduce the number of files in the root directory? (cosmetics)

[ImprovedTube]

side-effect: "used by: 899 people"-box (not making sense for this project)

[PTheocharis]

Hello 👋 Is there any update on the reviewing part?