[Feature] Email collect message hooks (#331)

- Add email collect hook on creating conversation
- Merge contact if it already exist

app/javascript/widget/api/endPoints.js

@@ -14,7 +14,12 @@ const getConversation = ({ before }) => ({
   params: { before },
 });
 
+const updateContact = id => ({
+  url: `/api/v1/widget/messages/${id}${window.location.search}`,
+});
+
 export default {
   sendMessage,
   getConversation,
+  updateContact,
 };