Chore: Add Facebook app set up documentation (#647)

Co-authored-by: Pranav Raj S <pranavrajs@gmail.com>

app/javascript/dashboard/api/channels.js

@@ -5,9 +5,9 @@
 import endPoints from './endPoints';
 
 export default {
-  fetchFacebookPages(token) {
+  fetchFacebookPages(token, accountId) {
     const urlData = endPoints('fetchFacebookPages');
     urlData.params.omniauth_token = token;
-    return axios.post(urlData.url, urlData.params);
+    return axios.post(urlData.url(accountId), urlData.params);
   },
 };