docs: add Decentralized Masternode Shares DIP#187

PastaPastaPasta wants to merge 2 commits into

dashpay:masterdashpay/dips:masterfrom

PastaPastaPasta:dip-pasta-shared-masternode-collateralPastaPastaPasta/dips:dip-pasta-shared-masternode-collateralCopy head branch name to clipboard