Add add_blacklist based on token symbol

[SheldonHH]

Currently add_blacklist function will add all token symbol based on this contract to the blacklist

bos.contracts/contracts/eosio.token/include/eosio.token/eosio.token.hpp

Line 88 in b641fc3

struct [[eosio::table]] account_blacklist

It will be great if we can add_blacklist based on token symbol