Add link to credential pre-encryption script

Author: simonrob

emailproxy.config

@@ -150,7 +150,8 @@ documentation = Accounts are specified using your email address as the section h
 		the service account method: there is essentially no local access control when creating new accounts. Using a
 		service account with the proxy in a publicly-accessible context is not advised. You are highly encouraged to
 		enable the proxy's secret encryption option (see `encrypt_client_secret_on_first_use` at the end of this file)
-		and consider pre-encrypting account entries.
+		and consider pre-encrypting account entries. A sample pre-encryption script is provided for reference at
+		https://github.com/simonrob/email-oauth2-proxy/issues/212#issuecomment-1867557029
 
 	Advanced account configuration:
 	- For most configurations the default `redirect_uri` value of `http://localhost` is correct, unless you have