update help function

main.py

@@ -25,6 +25,7 @@ USAGES = {
 \n        'length' = num characters in password \
 \n        'label' = optional name for the password \
 \n        'charset' = characters that can be in the password (use '-<characters>' to exclude a list of characters))\
+\n        Note: Available characters are 'l': lowercase, 'u': uppercase, 's': special, 'n': numbers, and 'w': words (take words from dictionary)
 ",
         "strength": "strength <password/label> - Evaluates the strength of a password, or if a label is provided then that password.",
         "echo": "echo <string content> ( 'string_content' = any text to be echoed )",