code: public StringTransformerChain extend(StringTransformerRule... additionalRules) {
  
      StringTransformerRule[] newRules = new StringTransformerRule[this.rules.length + additionalRules.length];
      System.arraycopy(this.rules, 0, newRules, 0, this.rules.length);
      System.arraycopy(additionalRules, 0, newRules, this.rules.length, additionalRules.length);
      return new StringTransformerChain(newRules);
    }
docs: This method extends this chain with {@code additionalRules}. <br>
  <b>ATTENTION:</b><br>
  If you want to be able to marshall the chain with JAXB, you have to use
  {@link StringTransformerChain#StringTransformerChain(String, StringTransformerChain, StringTransformerRule...)}
  instead.
  
  @param additionalRules are the rules to add.
  @return the chain that also checks the {@code additionalRules} if none of this rules match.