chore(Core/AchievementMgr): add GetAchievement helper (#6121)

src/server/game/Achievements/AchievementMgr.cpp

@@ -2962,3 +2962,8 @@ void AchievementGlobalMgr::LoadRewardLocales()
     LOG_INFO("server", ">> Loaded %lu Achievement Reward Locale strings in %u ms", (unsigned long)m_achievementRewardLocales.size(), GetMSTimeDiffToNow(oldMSTime));
     LOG_INFO("server", " ");
 }
+
+AchievementEntry const* AchievementGlobalMgr::GetAchievement(uint32 achievementId) const
+{
+    return sAchievementStore.LookupEntry(achievementId);
+}

src/server/game/Achievements/AchievementMgr.h

@@ -368,6 +368,9 @@ public:
     void LoadCompletedAchievements();
     void LoadRewards();
     void LoadRewardLocales();
+
+    [[nodiscard]] AchievementEntry const* GetAchievement(uint32 achievementId) const;
+
 private:
     AchievementCriteriaDataMap m_criteriaDataMap;