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.

2001/schweikh/README.md

@@ -81,3 +81,12 @@ straightforward; for '*' start out with '*foo' and 'foo*' against 'foo'.
 How does it deal with sequences of adjacent `*'? How could this be
 improved? If all else fails, recode the ?: operators with if/else and
 try again. For extra credit implement character classes like [a-z].
+
+## 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/