Update CMake configuration for auto-contained library installation

Dear @fandujar

I've made changes to the CMake configuration to enhance the portability and self-containment of our library installation. Instead of using CMAKE_SOURCE_DIR, I've updated the configuration to utilize PROJECT_SOURCE_DIR. This adjustment ensures that the default values for installing the targets are within the project directory, promoting a more self-contained and easily deployable library. Additionally, the configuration files will be well captured even if the library is automatically compiled by another CMake project.

This improvement makes it possible to utilize the fetch_content feature of CMake, thus making it easier for other developers to utilize the library.

Please review the changes and provide any feedback or suggestions for improvement. Thank you for your attention to this matter.