chore: add license & readme

Notesnook.API/Interfaces/IUserService.cs

@@ -1,3 +1,22 @@
+/*
+This file is part of the Notesnook Sync Server project (https://notesnook.com/)
+
+Copyright (C) 2022 Streetwriters (Private) Limited
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the Affero GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+Affero GNU General Public License for more details.
+
+You should have received a copy of the Affero GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
 using System.Threading;
 using System.Threading.Tasks;
 using Notesnook.API.Models.Responses;