message: added a rule append utility function
diff: @@ -201,6 +201,17 @@ export const debounce = (fn: () => any, wait: number = 0, immediate: boolean = f
  };
  };
  +export const appendRule = (rule, rules) => {
  + if (typeof rules === 'string') {
  + return `${rules}|${rule}`;
  + }
  +
  + return {
  + ...rules,
  + ...normalizeRules(rule)
  + };
  +};
  +
  /**
  * Normalizes the given rules expression.
  */
  