There are no instructions on how to do opencl-gl sharing in readme

There is an opencl-gl sharing test in full.csv, but it is turned off by default. And the lack of this explanation in readme, I think we can add some explanation.

for example:
This test also provides a test for the interaction between OpenCL and DirectX10,Direct11,OpenGL,OpenGL ES,Vulkan. If you want to do this test, you need to set it up on lines 30-34 of OpenCL-CTS/CMakeLists.txt.

For example: Open the OpenCL-GL sharing test.

option(GL_IS_SUPPORTED "Run OpenGL interop tests" ON)

Start by locating the README and the OpenCL-CTS/CMakeLists.txt entries around lines 30-34. Check the existing full.csv test description and the GL_IS_SUPPORTED option, then document how to enable the OpenCL-GL sharing test and what interop coverage it provides.

Written by the indexing model from the issue text.