Add Unit Tests for BumbleDocGen\Core\Renderer\Twig\Filter Namespace

[seanmcn]

Description:
It's crucial to ensure the code in the BumbleDocGen\Core\Renderer\Twig\Filter namespace is functioning properly. Here’s how you can contribute:

1. Write Tests:

   • Use PHPUnit to create tests for all classes and methods in this namespace.
   • Ensure the tests are thorough and follow the existing testing conventions in the project.

2. Run Tests Locally:

   • Execute composer run-script test to run the tests on your local machine and ensure they pass.

3. Create Pull Request:

   • Once ready, create a pull request to the 1.x.x branch with your tests.
   • GitHub will automatically run your tests again when you create the pull request.

4. Need Help?

   • If you encounter any issues or require assistance, comment on the issue and a maintainer will assist you.