Add a js-api attribute to opt-in to the YouTube Iframe Player API

[zachleat]

Allows using the getPlayer asynchronous method to access the player instance to control the video.

https://developers.google.com/youtube/iframe_api_reference#seekTo

Added an additional test/demo that shows usage examples.

Inspired by work on this stream: https://www.youtube.com/watch?v=MrVMewBq0jE

[paulirish]

she's a beauty! i have no nits, even.

thank you much @zachleat :D

[paulirish]

Danke!

[Stanzilla]

Demo errors with

Uncaught (in promise) TypeError: video.getPlayer is not a function
    at seekTo (js-api.html:17:27)
    at HTMLButtonElement.onclick (js-api.html:25:59)

[zachleat]

@Stanzilla looks like it was post-merge refactored as getYTPlayer.

@paulirish don’t forget to change README.md and variants/js-api.html too!

[zachleat]

(also, yay! thanks!)

[paulirish]

@Stanzilla looks like it was post-merge refactored as getYTPlayer.
@paulirish don’t forget to change README.md and variants/js-api.html too!

Yup yup. Thanks! missed these. 😊

Edit: all fixed and shipped a 0.3.2 just to make sure readme docs are good on npm.