Add mirror references back as historical note

Instead of having the mirror note in the YYYY/index.html files
completely removed it is back but as a historical note.

2001/README.md

@@ -8,10 +8,16 @@ on how to compile it and how to run the winning program.
 Look at the winning source and try to figure how it does what it does!
 You may then wish to look at the Author's remarks for even more details.
 
+
 Some ANSI C compilers are not quite as good as they should be.  If
 yours is lacking, you may need to compile using gcc instead of your
 local compiler.
 
+### Historical note:
+
+The IOCCC has a website and now has a number of international mirrors.  The
+primary site can be found at [www.ioccc.org](https://www.ioccc.org).
+
 
 ## Remarks on some of the entries