add quest exp modifier upgrade

src/components/UpgradesList.vue

@@ -3,6 +3,7 @@
     <h2>Upgrades</h2>
     <div class="upgrade">
       <span>Adventurer capacity (level {{ guild.adventurerCapacity.level }})</span>
+      <small>Increases the maximum amount of recruited adventurers</small>
       <button
           class="button metal"
           v-if="guild.adventurerCapacity.nextLevelCost"
@@ -12,6 +13,18 @@
         Upgrade ({{ formatGold(guild.adventurerCapacity.nextLevelCost) }} gold)
       </button>
     </div>
+    <div class="upgrade" v-if="guild.level >= guild.expModifier.guildLevelRequirement">
+      <span>Quest exp modifier (level {{ guild.expModifier.level }})</span>
+      <small>Increases exp from newly offered quests by 10% per level</small>
+      <button
+          class="button metal"
+          v-if="guild.expModifier.nextLevelCost"
+          :disabled="guild.gold < guild.expModifier.nextLevelCost"
+          @click="upgradeQuestExpModifier()"
+      >
+        Upgrade ({{ formatGold(guild.expModifier.nextLevelCost) }} gold)
+      </button>
+    </div>
   </section>
 </template>
 
@@ -39,7 +52,14 @@ export default defineComponent({
       if (this.guild.gold < this.guild.adventurerCapacity.nextLevelCost) return;
       this.guild.gold -= this.guild.adventurerCapacity.nextLevelCost;
       this.guild.adventurerCapacity.upgrade();
-    }
+    },
+    upgradeQuestExpModifier(): void {
+      if (!this.guild.expModifier) return;
+      if (!this.guild.expModifier.nextLevelCost) return;
+      if (this.guild.gold < this.guild.expModifier.nextLevelCost) return;
+      this.guild.gold -= this.guild.expModifier.nextLevelCost;
+      this.guild.expModifier.upgrade();
+    },
   }
 });
 </script>
@@ -63,12 +83,15 @@ export default defineComponent({
     font-size: 1.25rem;
     font-weight: bold;
     display: flex;
-    flex-direction: row;
-    flex-wrap: wrap;
+    flex-direction: column;
     width: min(25rem, 100%);
     justify-content: center;
     align-items: center;
     gap: 0.2rem;
+    small {
+      font-weight: normal;
+      line-height: 1;
+    }
   }
 }
 </style>