elm_config: Add doc for the new depth/stencil/msaa preference
elm_config: Add doc for the new depth/stencil/msaa preference

rvandegrift/elementary,FlorentRevest/Elementary,rvandegrift/elementary,FlorentRevest/Elementary,tasn/elementary,tasn/elementary,tasn/elementary,FlorentRevest/Elementary,rvandegrift/elementary,tasn/elementary,FlorentRevest/Elementary,rvandegrift/elementary,tasn/elementary