Kind of basic right now.

Three functions to hook. All functions should pass through as they do (kind of) important work.

EnemyBuffs_BuffsAdded(buffName) - gets called when a buff is added to the target (note that this may mean refreshing of a buff, e.g. no change to the list)
EnemyBuffs_BuffsRemoved(buffName) - gets called when a buff is removed from the target
EnemyBuffs_TargetChanged() - gets called when the target changes

These variables are accessible (and will remain so):
EnemyBuffs_Buffs - contains a list of the names of the buffs currently on the target