DOC: Add CONTRIBUTING.md
DOC: Add CONTRIBUTING.md

abouteiller/ucx,shssf/ucx,sergsagal1/ucx_rocm,abouteiller/ucx,shssf/ucx,shssf/ucx,sergsagal1/ucx_rocm,abouteiller/ucx,sergsagal1/ucx_rocm,abouteiller/ucx