Add Contributing guide
Add Contributing guide

IanMayo/january,SmithRWORNL/january,yannick-mayeur/january,SmithRWORNL/january,yannick-mayeur/january,yannick-mayeur/january,IanMayo/january,SmithRWORNL/january,IanMayo/january,yannick-mayeur/january,IanMayo/january