Adding CLA first version to CONTRIBUTING.md
Adding CLA first version to CONTRIBUTING.md

[ci-ignore]
FabienPean/sofa,FabienPean/sofa,FabienPean/sofa,FabienPean/sofa,FabienPean/sofa,FabienPean/sofa,FabienPean/sofa,FabienPean/sofa,FabienPean/sofa,FabienPean/sofa