added quest gold modifier upgrade

src/classes/guildUpgrades/QuestGoldUpgrade.ts

@@ -0,0 +1,24 @@
+import {GuildUpgrade} from "@/classes/GuildUpgrade";
+
+export default class QuestGoldUpgrade extends GuildUpgrade {
+  constructor(level: number = 1) {
+    super();
+    this.level = level;
+    this.nextLevelCost = this.getCostForLevel(this.level);
+    this.guildLevelRequirement = 8;
+  }
+
+  upgrade(): void {
+    this.level += 1;
+    this.nextLevelCost = this.getCostForLevel(this.level);
+  }
+
+  getCostForLevel(level: number): number {
+    const scalingFactor = Math.pow(1.05, level - 1);
+    return Math.floor(2500000 * scalingFactor * Math.pow(level, 1.01));
+  }
+
+  getModifier(): number {
+    return 1 + (this.level * 0.1);
+  }
+}