Allow reduced privacy embeds

[Garbee]

Spawning from discussion in #80

Currently the lite embed only works in the enhanced privacy mode. Since the URL is hard-coded to use the "no cookie" serving. This can cause potential problems with some types of content if a publisher allows it to be embedded while being protected by a paywall for example.

A new attribute should be introduced which will remove the no cookie from the iframe URL. My personal preference is calling it reduced-privacy which is directly opposite of the default of using what YouTube calls "Enhanced Privacy".

The attribute, regardless of final name, should be a boolean attribute. Meaning it's presence alone triggers the effect and any values assigned are ignored.