Add domain filtering

[sanyamjain47]

This pull request introduces enhancements to the perplexity-ask tool, adding new features like domain filtering and model selection, while also updating dependencies and documentation. The changes focus on improving functionality, flexibility, and developer usability.

Tool Enhancements:

• Added support for search_domain_filter in perplexity_ask, perplexity_research, and perplexity_reason tools to limit or denylist search domains. This parameter accepts up to 10 domains. [1] [2] [3]
• Introduced optional model parameter for perplexity_ask and perplexity_reason tools, allowing users to specify models like sonar, sonar-pro, sonar-reasoning, or sonar-reasoning-pro. Defaults are provided for each tool. [1] [2]

Code Updates:

• Updated performChatCompletion function to handle search_domain_filter and validate the number of domains. Added logic to prioritize user input, environment variables, and defaults for domain filtering. [1] [2]
• Improved error handling and validation for tool arguments, ensuring robust input checks for models and domain filters. [1] [2]

Documentation Improvements:

• Expanded README.md to include details on domain filtering and model selection, along with environment variable setup instructions for PERPLEXITY_SEARCH_DOMAIN_FILTER. [1] [2]

Dependency Updates:

• Added new dependencies like axios and dotenv to enhance API handling and environment variable support. Updated @types/node and other packages to their latest versions. [1] [2] [3]

These changes collectively improve the functionality and usability of the perplexity-ask tool for developers and end-users.