Provide cmake-package
Hello,

Maintaining [conda-forge/glad-feedstock](https://github.com/conda-forge/glad-feedstock) is my goal (https://github.com/conda-forge/glad-feedstock/issues/7).

But I have an idea how to improve CMake support in upstream.
What do you think about translating [cmake/CMakeLists.txt](https://github.com/Dav1dde/glad/blob/glad2/cmake/CMakeLists.txt) into GladConfig.cmake?

To ensure backward compatibility, we can set CMAKE_PREFIX_PATH to a new location of GladConfig.cmake and enable the use of python module from sources inside cmake/CMakeLists.txt.

If it's okay with you, I can provide PR.
