add simple wpt demo

[fippo]

I couldn't think of anything useful so I'm just outputting the "frame" (including padding) via console.table

[jlaine]

Feel free to completely gut the HTML + JS I wrote, it's not my finest work. In other words : you don't necessarily need a separate wpt.html, I'm fine with replacing index.html

[fippo]

updated. I must resist adding something that sends a copy of the stun packets to the client :-)

[jlaine]

Let me know when you're happy with me hitting the merge button, or even move this repo to shared ownership

[fippo]

:raised_hands: -- long-term plan would be to make this repository obsolete and the tests available in web-platform-tests but lets use it as a staging ground for now