chore: update Testing Guidelines with MSTest

Author: DevTKSS

CONTRIBUTING.md

@@ -8,7 +8,7 @@ Thank you for your interest in contributing! We welcome contributions from the c
 
 1. **Fork the repository** and create your branch from [`development`](https://github.com/MapsterMapper/Mapster/tree/development)
 2. **Make your changes** following the existing code style
-3. **Write tests** using [xUnit](https://xunit.net/) to ensure your changes work correctly
+3. **Write tests** using [MSTest](https://docs.microsoft.com/en-us/dotnet/core/testing/unit-testing-with-mstest) and [xUnit](https://xunit.net/) to ensure your changes work correctly
 4. **Document your code** with XML comments and update [docs/articles/](./docs/articles/) if needed following the [DocFX](https://dotnet.github.io/docfx/) guidelines
 5. **Commit with clear messages** following [Conventional Commits](https://www.conventionalcommits.org/en/v1.0.0/) (e.g., `feat:`, `fix:`, `docs:`)
 6. **Submit a pull request** with a description of your changes