Implement HTML5 ads support (+fallback)

[dmngdsm]

We need to implement Interactive & Rich HTML5 ads format support as some advertisers requested it and all leading ad networks support it. HTML5 ads will allow advertisers to implement real CTA buttons or creative animations, etc.

This will also apply to fallback tags by default

[Ivshti]

@dmngdsm can you give me a few example tags that I can test with?

[Ivshti]

may assign this to @rori4 if I don't get to it