Allow attributes to be added to Doubleclick AMP ad units' markup

[dero]

Currently, the AMP markup for doubleclick ad units has a firm structure that doesn't allow 3rd parties to change the generated markup (AFAIK, let me know if this is incorrect).

In our case we're running a native AMP site and would like to create a child theme and change the units' markup to potentially contain rtc-config and / or data-multi-size attributes to increase ad demand competition, but we're unable to easily do so.

Would it be possible to make the generated AMP ad unit string filterable? Or do you consider a filter like that to be too powerful and we should look for other options?

[kmwilkerson]

Closing this issue as Newspack is in the process of moving away from AMP