Updated Appendix A: Test Sites (markdown)

Appendix-A:-Test-Sites.md

@@ -72,6 +72,7 @@ If you would like to submit a test page to be added to this list, please post th
    * disable JS, resize the browser with the tests open
    * [@media window size leak PoC](https://demos.traudt.xyz/css/media/index.html) - **h**ttps://demos.traudt.xyz/css/media/index.html
    * [Inner Window Measurements](https://arthuredelstein.github.io/tordemos/media-query-fingerprint.html) - **h**ttps://arthuredelstein.github.io/tordemos/media-query-fingerprint.html
+ - [IPv6 Leak](http://ipv6leak.com/) - **h**ttp://ipv6leak.com/
 - [Keyboard Events](https://w3c.github.io/uievents/tools/key-event-viewer.html) - **h**ttps://w3c.github.io/uievents/tools/key-event-viewer.html
 - [Popup Killer](http://www.kephyr.com/popupkillertest/index.html) - **h**ttp://www.kephyr.com/popupkillertest/index.html
 - [Popup Test](http://www.popuptest.com/) - **h**ttp://www.popuptest.com/