Added Unit Tests for Counters Lesson in Repetitions Chapter

[its-ChaTTy]

Summary

Added Unit Tests for Counters Lesson in Repetitions Chapter (TWP15_3) in both English & Spanish Version. Tries to fix Issue #245.

Checklist

• [x] Variables, functions and comments are translated to Spanish
• [x] Functions follow underscore notation
• [x] Spell check done & typos fixed
• [x] All python code is PEP8 compliant
• [x] Test coverage with Playwright implemented; locators are Pyhton code
• [x] Reviewers assigned (all peers & at least 1 mentor)

Screenshots

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