feat: added the global timeout feature for the entire process

[Manav-Desai-07]

This PR introduces a global timeout feature for Sitemapper. The new globalTimeout option allows developers to set a maximum overall execution time for sitemap parsing. This prevents the process from running indefinitely, especially when encountering irregular or malformed sitemaps.

Changes

• Added globalTimeout configuration option in the Sitemapper constructor.
• Updated the fetching logic to abort ongoing requests if the global timeout is reached.
• Added examples in the documentation for both Promise and Async/Await usage demonstrating the global timeout feature.
• Updated README.md with new globalTimeout usage examples and notes.

Benefits:

• Prevents infinite loops or hanging processes due to irregular sitemap structures.
• Provides developers with greater control over resource usage and execution timing.
• Enhances reliability for automated workflows or cron jobs using Sitemapper.