feat: Add 4 methods (#158)

1:
Player:GetAchievementPoints

2:
Player:GetCompletedQuestsCount
This should have been GetCompletedQuestsCount, not sure how to update that now.

3: You also have an option to include feats of strength or not (not included by default, blizzard like)
Player:GetCompletedAchievementsCount

4: RegisterPlayerEvent
OnCreatureKilledByPet

src/LuaEngine/LuaEngine.h

@@ -490,6 +490,7 @@ public:
     bool OnCanGroupInvite(Player* player, std::string& memberName);
     void OnGroupRollRewardItem(Player* player, Item* item, uint32 count, RollVote voteType, Roll* roll);
     void OnBattlegroundDesertion(Player* player, const BattlegroundDesertionType type);
+    void OnCreatureKilledByPet(Player* player, Creature* killed);
 
 #ifndef CLASSIC
 #ifndef TBC