add clarification for "cryptographic security"

No matter how nice they are, under no
circumstances should keymashes be used as a source
of randomness for cryptographic purposes.

README.md

@@ -2,7 +2,9 @@
 
 Finally, it is here: The gay keymash device driver!
 It provides an endless supply of lowercase characters from the
-QWERTY home row in a cryptographically secure random order.
+QWERTY home row in a cryptographically secure random order¹.
+
+¹ **Do not** actually use this as a source for randomness, at least not for crypto purposes.
 
 ## IMPORTANT!