Function appendChildren should add a new child div to each existing div. New divs should be decorated by calling decorateDiv.
For example, after appendChildren is executed, the following divs:
<div id="a"> <div id="b"> </div> </div>
should take the following form (assuming decorateDiv does nothing):
<div id="a"> <div id="b"> <div></div> </div> <div></div> </div>
The code below should do the job, but for some reason it goes into an infinite loop. Fix the bugs.