Modernize contextMenus sample to use Google Search parameters instead…

[Shreyans-704]

Closes #1653

Summary

Update the global_context_search sample to reflect modern Google Search behavior. The previous implementation relied on domain-based localization (e.g., google.ca, google.co.jp), which no longer affects search results.

Changes

• Replace domain-based URLs with a single base: https://www.google.com/search
• Add query parameters for region specificity:
  • cr (country restriction): e.g., countryCA, countryJP, countryRU
  • lr (language restriction): e.g., lang_en, lang_ja, lang_ru
• Refactor locales.js into a structured regions configuration object
• Improve code clarity and maintainability
• Add inline documentation explaining modern search behavior
• Update README to reflect current best practices

Why

Modern Google Search localizes results primarily based on IP geolocation, making domain-based localization ineffective. Using cr and lr parameters provides a more accurate and programmatic way to demonstrate regional search differences.

Testing

• Loaded extension locally in Chrome
• Verified context menu behavior
• Confirmed region-specific search results differ as expected

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