Add a "Installation Successful" Screen to Duplicate Post

[BobBreukhoven]

https://yoast.atlassian.net/browse/DUPP-70

Like Yoast SEO Premium, Duplicate post should get a post-install"Installation Successful" page.

This page should highlight the most important features of Duplicate Post, with text and images. A quick show of what features our users just added to their arsenal. Additionally: there should be a section where we ask users to:

• Sign up for the newsletter
• Opt-in for tracking

Will probably be a mini-epic.

Needs decisions from Product and design from UX.

Maybe combine with DUPP-69: Add opt-in data collection to Duplicate PostTO DO.