feat: Add store for conversation watchers (#5808)

Co-authored-by: Pranav Raj S <pranav@chatwoot.com>

app/javascript/dashboard/api/inbox/conversation.js

@@ -105,6 +105,16 @@ class ConversationApi extends ApiClient {
       custom_attributes: customAttributes,
     });
   }
+
+  fetchParticipants(conversationId) {
+    return axios.get(`${this.url}/${conversationId}/participants`);
+  }
+
+  updateParticipants({ conversationId, userIds }) {
+    return axios.patch(`${this.url}/${conversationId}/participants`, {
+      user_ids: userIds,
+    });
+  }
 }
 
 export default new ConversationApi();