nicobermani Extend.NET .cursorrules file for C#

Here's a description of the existing project to understand the context and how to approach future work with C# best practices:

• Project Overview:
  - Name: Extend.NET
  - Purpose: Provide reusable extension methods and helpers for .NET developers
  - Structure: Multiple sub-projects for different categories (e.g., String, File)

• Project Structure:
  - src/Directory.Build.props: Common properties for all sub-projects
  - src/Extend.NET.File: File-related extensions
  - src/Extend.NET.String: String-related extensions
  - .github/workflows/publish-nuget.yml: CI/CD pipeline for building and publishing

- Targets all versions of .NET.

Within each project, the following rules apply:
  This project contains only extension methods related to Math.
  Each file should use partial class MathExtensions.
  Each file should have single .net extension method. 
  Each filename should be the name of the method it contains.
  Use the `this` keyword for the first parameter to make it an extension method.
  Add XML documentation comments for the method, describing its purpose, parameters, and return value.
  All files should be defined in root directory.