Update .DEREK maintainers list
Update .DEREK maintainers list

Add `ivanayov` to .DEREK

Signed-off-by: Ivana Yovcheva <86e73595f14df5226ef437d57671288872a8681c@vmware.com>

openfaas-incubator/of-watchdog,openfaas-incubator/of-watchdog