Add wait_until_ready implementation for Meta chatbot

- in meta, implement wait for input element

└── apps
    └── browser
        └── src
            └── content-scripts
                └── send-prompt-content-script
                    └── chatbots
                        ├── ai-studio.ts
                        ├── arena.ts
                        ├── chatgpt.ts
                        ├── claude.ts
                        ├── copilot.ts
                        ├── deepseek.ts
                        ├── doubao.ts
                        ├── gemini.ts
                        ├── github-copilot.ts
                        ├── grok.ts
                        ├── hugging-chat.ts
                        ├── index.ts
                        ├── kimi.ts
                        ├── meta.ts
                        ├── mistral.ts
                        ├── open-webui.ts
                        ├── openrouter.ts
                        ├── qwen.ts
                        ├── together.ts
                        ├── yuanbao.ts
                        └── z-ai.ts

Author: robertpiosik

apps/browser/src/content-scripts/send-prompt-content-script/chatbots/meta.ts

@@ -6,6 +6,22 @@ import {
 import { report_initialization_error } from '../utils/report-initialization-error'
 
 export const meta: Chatbot = {
+  wait_until_ready: async () => {
+    await new Promise((resolve) => {
+      const check_for_element = () => {
+        if (
+          document.querySelector(
+            'button[data-testid="composer-mode-dropdown-button"]'
+          )
+        ) {
+          resolve(null)
+        } else {
+          setTimeout(check_for_element, 100)
+        }
+      }
+      check_for_element()
+    })
+  },
   enter_message: async (params) => {
     const input_element = document.querySelector(
       'div[contenteditable="true"][data-testid="composer-input"]'