on method
void
on(})
Implementation
void on(String command, Function(String string, List<String> args) handler, {RegExp? validator, String? usage, List<String>? aliases, List<String>? similar}) {
final CommandHandler commandHandler = CommandHandler(
function: handler,
validator: validator,
usage: usage,
);
handlers[command] = commandHandler;
if (aliases != null) for (final String alias in aliases) handlers[alias] = commandHandler;
if (similar != null) for (final String str in similar) this.similar[str] = command;
}