git commit --amend -m"Create cmake-multi-platform

git commit --amend -m "Create cmake-multi-platform.yml

This commit introduces a new GitHub Actions workflow configuration file named 'cmake-multi-platform.yml'. The purpose of this workflow is to automate the build and test processes for a CMake project across multiple platforms, specifically Ubuntu and Windows.

Key Changes and Improvements:
- Workflow Name: CMake on multiple platforms
- Trigger Events: The workflow is triggered on push and pull request events to the 'main' branch.
- Job Strategy: The 'build' job runs on a matrix of operating systems (Ubuntu, Windows) and compilers (GCC, Clang, MSVC). The matrix strategy ensures that the build and tests are executed for all specified combinations. Fail-fast is set to false to ensure feedback is delivered for all matrix combinations.

Steps Included:
1. Checkout Code: Uses the 'actions/checkout@v4' to checkout the repository.
2. Set Reusable Strings: Defines and sets reusable strings for directory paths.
3. Configure CMake: Configures CMake in a 'build' subdirectory with appropriate compiler settings.
4. Build: Builds the project using CMake with the specified configuration.
5. Test: Executes tests defined by the CMake configuration using 'ctest'.

Benefits and Impacts:
- This workflow enhances the CI/CD pipeline by ensuring that the project is built and tested across different platforms and compilers, increasing the robustness and reliability of the software.
- Automates the build and test processes, reducing manual intervention and potential errors