put all README.md files under CC BY-SA 4.0 License

This will make is easier for others to share README.md
files while requiring them to attribute the file
when using it.

2005/chia/README.md

@@ -54,3 +54,12 @@ The code requires a preprocessor that can stomach all kinds of nonsense that
 are passed as parameters to macros for stringification. GNU cpp handles such
 things just fine, but certain broken preprocessors may decide to freak out
 when they see macro parameters that don't look like C tokens.
+
+## Copyright and CC BY-SA 4.0 License:
+
+This file is Copyright (c) 2023 by Landon Curt Noll.  All Rights Reserved.
+You are free to share and adapt this file under the terms this license:
+
+    Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
+
+For more information, see: https://creativecommons.org/licenses/by-sa/4.0/