Add commands.config.usage_hint

bot/en.json

@@ -11,6 +11,7 @@
         "config": {
             "title": "Configuration",
             "unknown_setting": "Unknown setting \"{{setting}}\"",
+            "usage_hint": "Use **{{command}} <option> <new value>** to change a setting, or use **clear** as value to reset it.",
             "setting_info": {
                 "title": "Setting: {{setting}}",
                 "type": "Type: {{type}}",