Create a Media Linker Plugin

[utsab]

We would like to illustrate a plugin within the otio-youtube-example. Plugins are an interesting concept within OTIO which may be confusing to understand for newbies. If we can show a concrete example of a plugin within our repo, we could help to clarify what a plugin is, how it is used, and how to create one.

Here is some feedback from Joshua Minor on a possible direction we can explore to create a plugin:

"... make a Media Linker plugin which looks at individual clips in an OTIO, and if they point to a YouTube URL, it could pull metadata & markers into the clip from YouTube."

https://opentimelineio.readthedocs.io/en/latest/tutorials/write-a-media-linker.html