Add section on renderer.options

[matthewlane]

Docs update for prebid/Prebid.js#2025

[rmloveland]

Hey @matthewlane is my reading of the PR correct, that you pass arbitrary properties to the renderer, so it depends on what the renderer accepts/understands?

Given that, is renderer.options.adText an actual property we should document, or just an example?

[matthewlane]

That's correct, arbitrary properties are passed to the renderer, and it depends on what the renderer understands. AppNexus's renderer does understand adText, but this isn't necessarily a universally understood renderer property. Not sure weather all of the AppNexus properties should be documented or not. If it would be more clear I can change adText to something non-AppNexus specific

[rmloveland]

No need to update, thanks @matthewlane - just want to make sure I understand it so I can eventuallly add to the (eventual) ad unit reference which is still a baby PR here: #558

[rmloveland]

Thanks @matthewlane !