Tell about wordlist location in manpage.

Avoid to write down a certain path, as that could block reproducible
builds.

docs/manpage.rst

@@ -78,6 +78,10 @@ files
 `~/.diceware.ini`
     Your personal diceware configuration file.
 
+``diceware`` also comes with a set of wordlists. The path where these lists are
+stored is showed with ``--help``.
+
+
 copyright
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