Add some detail to testdata/README.md
@@ -20,5 +20,8 @@ waives any copyright it might have, for any purpose, including commercial and
noncommercial use, free of charge and without requiring permission from the
Museum."
+pi.txt contains the digits of pi. The *.giflzw file was generated by
+script/compress-giflzw.go
+
pjw-thumbnail.* are various encodings of an image derived from an iconic,
original photo of Peter J. Weinberger by Rob Pike <r@golang.org>.
