docs: comprehensive cache control documentation for Ariadne example

[nogueira-raphael]

Summary

Comprehensive update to the Ariadne example README documenting all @cacheControl directive scenarios from Apollo Server caching documentation.

Changes

• Translated to English (was in Portuguese)
• Added Table of Contents for easy navigation
• Documented all @CacheControl scenarios:
  • Field-level definitions (@cacheControl(maxAge: 300))
  • Type-level definitions (type User @cacheControl(maxAge: 600))
  • Field overriding type-level settings
  • inheritMaxAge usage and when to use it
  • Dynamic cache hints in resolvers (set_cache_hint, private_cache, no_cache)
• Explained cache behavior calculation:
  • Lowest maxAge wins
  • PRIVATE wins over PUBLIC
• Documented default maxAge behavior:
  • Root fields default to 0
  • Non-scalar fields default to 0
  • Scalar fields inherit from parent
• Added example queries with expected Cache-Control headers
• Documented cache invalidation patterns

Closes

Partially addresses #6 (Improve FastAPI + Ariadne example)

Reference

Based on: https://www.apollographql.com/docs/apollo-server/performance/caching/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.55%. Comparing base (32a0c6f) to head (1b79047).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #18   +/-   ##
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  Coverage   71.55%   71.55%           
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  Files          34       34           
  Lines        1030     1030           
  Branches      163      163           
=======================================
  Hits          737      737           
  Misses        254      254           
  Partials       39       39           

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