adding donate button

README.md

@@ -5,6 +5,13 @@
 
 This is a gentle step-by-step guide through the abstract and complex universe of Fragment Shaders.
 
+<form action="https://www.paypal.com/cgi-bin/webscr" method="post" target="_top">
+<input type="hidden" name="cmd" value="_s-xclick">
+<input type="hidden" name="hosted_button_id" value="B5FSVSHGEATCG">
+<input type="image" src="https://www.paypalobjects.com/en_US/i/btn/btn_donate_SM.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
+<img alt="" border="0" src="https://www.paypalobjects.com/en_US/i/scr/pixel.gif" width="1" height="1">
+</form>
+
 ## Contents
 
 * [About this book](00/)
@@ -26,6 +33,7 @@ This is a gentle step-by-step guide through the abstract and complex universe of
     * Random
     * Noise
     * Fractional brownian motion
+    * Fractals
 
 * Image processing:
     * What is a texture?