[css-text] Add example of stretching Arabic with 'letter-spacing'.

PNGs created with the following code:

<!-- Rendered with Firefox 29, assuming bugs therein -->
<!DOCTYPE html>
<style>
pre { font: 30px KacstOne; margin: 0; text-align: center;}
span { letter-spacing: 0.5em; }
pre { float: left; border: silver; border-style: none solid; position: relative; }
div { position: absolute; right: -2em; }
no { color: red; }
ok { color: green; }
</style>
<pre>
الإبداع المتجدد
<no><span>الإبداع المتجد</span>د</no>
<ok>الإبـــــــــــــداع المتــــــــــــــجـــــــــــــدد</ok>
<ok>الإبـــــــــــداع   المتــــــــــــجــــــــــــدد</ok>
<ok>الإبداع   المتجدد</ok>
<no>ا لإ بد ا ع  ا لمتجد د</no>
[css-text] minor clarification to letter-spacing cursive