demo.html - Added Linux instructions for zoom

demo.html

@@ -95,6 +95,9 @@
 					<p>
 						Hold down alt and click on any element to zoom in on it using <a href="http://lab.hakim.se/zoom-js">zoom.js</a>. Alt + click anywhere to zoom back out.
 					</p>
+					<p>
+						(NOTE: Use ctrl + click in Linux.)
+					</p>
 				</section>
 
 				<section>