Add video integration

[mitchelloharawild]

cc @cynthiahqy Video for module is specified in metadata, via youtube link which is embedded at the top of the page.

Stretch goals:

• Floating / PiP layout for video after scrolling
• Timecode attribute of headers to automatically navigate through exercises along with video
• Video pause/play/next timecode buttons

[mitchelloharawild]

Embed with https://github.com/paulirish/lite-youtube-embed

[mitchelloharawild]

Example with code available: https://tutsplus.github.io/how-to-create-a-sticky-floating-video-on-page-scroll/