Add alternative bottle pluralization solution and update README TOC

[kagandavran]

Summary

• Adds a second solution for the bottle pluralization exercise that correctly
  handles singular/plural forms of “bottle”.
• Updates the README table of contents to include a link to this new solution.

Why

• Provides learners an additional approach while staying within the concepts
  taught in class up to this point.
• Improves discoverability via the README TOC.

Notes

• The existing solution(s) remain unchanged.
• The new solution uses only concepts covered so far in the course (no advanced
  libraries or features).

Quick check

• For count = 1 → output uses “bottle”
• For count ≠ 1 → output uses “bottles”