Q4 pricing and prospectus

[davidfischer]

• Increases some prices (mostly North America)
• New prospectus with niche targeting slide
• Adds niche targeting to pricing matrix
• TODO: we probably want a niche targeting explainer page

[davidfischer]

Yea, we have the blog posts and the demo page, but should probably do a landing page or similar?

I was thinking we'd replace the "hiring developers" section under audiences with niche targeting. Or possibly put niche targeting first. Then have a landing page describing it with a link to the "try it" page.

[davidfischer]

I added the explainer page in https://github.com/readthedocs/ethicalads.io/pull/454.