Add named equipment rewards

tools/validate_data.ps1

@@ -96,6 +96,7 @@ $validTriggers = @("battle_start", "battle_begin", "turn_start", "unit_reaches_t
 $validActions = @("log", "dialogue", "set_objective", "grant_item", "grant_items", "spawn_deployment", "spawn_deployments")
 $validEffects = @("heal_hp", "heal_mp", "cure_status")
 $validItemKinds = @("weapon", "armor", "accessory", "consumable")
+$validItemRarities = @("common", "named")
 $validBonusStats = @("hp", "mp", "atk", "def", "int", "agi")
 $validSkillKinds = @("damage", "heal", "support")
 $validSkillTargets = @("enemy", "ally", "self", "any")
@@ -703,6 +704,12 @@ function Check-Item-Effects() {
         if ([int](Get-Prop $item "price" 0) -lt 0) {
             Fail "Item $itemId has negative price."
         }
+        if (Has-Prop $item "rarity") {
+            $rarity = [string](Get-Prop $item "rarity" "")
+            if (-not $validItemRarities.Contains($rarity)) {
+                Fail "Item $itemId has unknown rarity: $rarity"
+            }
+        }
         if ($kind -eq "weapon") {
             if (-not (Has-Prop $item "weapon_type")) {
                 Fail "Weapon item $itemId is missing weapon_type."