chore: document slug using JSDoc

[tkrotoff]

Description

I suggest to put as much documentation as possible in JSDoc (FYI Playwright does this very well)

That's so convenient to have the documentation right into the IDE

• [X] I have read and understand the CONTRIBUTING.md document in this repository.

Type of change

• [X] Chore (non-breaking change which does not add functionality)
• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Change to the templates directory (does not affect core functionality)
• [ ] Change to the examples directory (does not affect core functionality)
• [ ] This change requires a documentation update

Checklist:

• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] Existing test suite passes locally with my changes
• [ ] I have made corresponding changes to the documentation

[github-actions[bot]]

This PR is stale due to lack of activity.

To keep the PR open, please indicate that it is still relevant in a comment below.

[tkrotoff]

I prefer a review than a stupid bot that automatically closes PR