Add QueryBallPoint

[LatteCoconut]

Title: Add QueryBallPoint Method for n-Dimensional Range Searching

Description: What changes were made? Implemented QueryBallPoint method: This method allows querying all points within a specified radius from a given point in the KDTree, enhancing the tree's capabilities for n-dimensional range searching.

Added comprehensive tests: To ensure reliability and performance, added unit tests covering various scenarios for the QueryBallPoint method.

Updated documentation: Expanded the README.md with a new section detailing usage examples and benefits of the QueryBallPoint method, making it easier for new users to understand its purpose and how to use it.

Why were these changes made? The motivation behind adding the QueryBallPoint method was to provide an efficient way to perform range searches in multi-dimensional spaces. This functionality is particularly useful in applications requiring spatial queries, such as GIS systems, gaming, and machine learning data structures, where quick retrieval of points within a certain distance from a target point is needed.

How were the changes tested? The added unit tests cover several scenarios, including:

Querying points within different radii from a target point Edge cases where no points are within the target radius Performance with a large number of points in high-dimensional spaces These tests ensure that the QueryBallPoint method works as expected and maintains the performance standards of the KDTree implementation.

I'm not very good at English, the above was translated by me using chatgpt