Refactor message handling by creating dedicated handlers for rule34 and yandere plugins, and add default string utility function

src/bot.ts

@@ -1,5 +1,5 @@
 import { createBot, Intents, startBot } from "npm:discordeno@18.0.1";
-import { messagehandler } from "./messages.ts";
+import { yandereMessageHandler } from "./messages.ts";
 
 const BOT_TOKEN = Deno.env.get("BOT_TOKEN") ?? "";
 if (!BOT_TOKEN) {
@@ -14,7 +14,7 @@ const bot = createBot({
       console.log("Bot is ready!");
     },
     async messageCreate(bot, message) {
-      await messagehandler(bot, message);
+      await yandereMessageHandler(bot, message);
     }
   }
 });