add test coverage badge with Coveralls

[ahasunos]

We need to integrate a test coverage badge into our repository using Coveralls. Since Coveralls only supports public repositories for free, we should implement this once the repository is made public.

Tasks:

1. Set up Coveralls:

• Create an account on Coveralls if not already done.
• Link the repository with Coveralls.
• Configure Coveralls in the Repository:

2. Update the .github/workflows/test.yml file to include Coveralls configuration.

• Ensure the test coverage report is being sent to Coveralls.
• Add Coverage Badge:

3. Retrieve the badge URL from Coveralls.

• Add the badge to the README file.

4. Verify Integration:

• Ensure that the badge updates correctly after test runs.