Add Support for Custom Distance Metrics

[nickna]

Description:

Enhance Neighborly by adding support for custom distance metrics in search algorithms, providing more flexibility for different use cases.

Tasks:

• Modify the existing search algorithms to accept custom distance metrics.
• Implement several common custom distance metrics as examples (e.g., Manhattan distance, Minkowski distance).
• Write unit tests to ensure the correctness and flexibility of the custom distance metric implementation.

Resources:

• Distance Metrics
• Existing search algorithm implementations in Neighborly

Impact:

Support for custom distance metrics will make Neighborly more versatile and adaptable to various application requirements.

How to Contribute:

1. Fork the repository and create a new branch for your changes.
2. Implement the support for custom distance metrics.
3. Ensure all new and existing tests pass.
4. Submit a pull request with a detailed description of the changes.