README.md: re-format; update license text

Signed-off-by: Maciej Barć <xgqt@riseup.net>

README.md

@@ -1,3 +1,5 @@
+# Scripts
+
 <p align="center">
     <a href="https://gitlab.com/src_prepare/scripts/pipelines">
         <img src="https://gitlab.com/src_prepare/scripts/badges/master/pipeline.svg">
@@ -20,6 +22,30 @@
 </p>
 
 
-# Scripts
+# About
 
 Miscellaneous maintenance scripts by src_prepare group
+
+
+# License
+
+SPDX-License-Identifier: GPL-3.0-only
+
+## Unless otherwise stated contents here are under the GNU GPL v3 license
+
+This file is part of scripts.
+
+scripts is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, version 3.
+
+scripts 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
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with scripts.  If not, see <https://www.gnu.org/licenses/>.
+
+Copyright (c) 2020-2021, src_prepare group
+Licensed under the GNU GPL v3 License