Add dropdown to /inventory command for quick navigation (#365)

- Add ability to handle dropdown menus with the bot
- Add a dropdown to the inventoryhelper
- Add handler for the dropdown to navigate to that page

#344

Reviewed-on: #365
Reviewed-by: VylpesTester <tester@vylpes.com>
Co-authored-by: Ethan Lane <ethan@vylpes.com>
Co-committed-by: Ethan Lane <ethan@vylpes.com>

src/type/stringDropdownEvent.ts

@@ -0,0 +1,5 @@
+import {StringSelectMenuInteraction} from "discord.js";
+
+export abstract class StringDropdownEvent {
+    abstract execute(interaction: StringSelectMenuInteraction): Promise<void>;
+}