Update Plugin Params Docs

As the :bird: :man: says, it's time to "thicken those data webs!"

This PR:

* Combines oEmbed docs and Embed API docs
* Rolls all Embed Params together, and then rolls THAT into the Embed Options doc
* Adds some notes around how customize has affected this.

Gonna :rocket:, but peeps read it over and let me know how we can make this even better!!!