Added the new item "Garrison Shield"

A new item "Garrison Shield" has been added. If a unit has it, the enemy's and the unit's own AS are reduced to 0 in combat. This item cannot be traded on the map.

This item has the same effect as the skill in FE14, "Wary Fighter". Since the AS of both sides is 0, there will be no Pursuit or Adept in that battle. I thought about implementing it as a skill, but I decided to implement it as an item because a non-detachable skill with a disadvantage should not be implemented.

Items that cannot be traded on the map cannot be stolen. To take something that an enemy has, you must use the Thief staff.