Recover embed examples

fixes #1458 

This recover the embed examples: 2 scripts and the reveal-based flask-based embed-based application :wink:

I just opened this as an standalone PR because it is a group of related examples and I am reintroducing them as a whole, not just tiny fixes like we will push to the pre-release example PR.
> Yeap, thanks for clarifying. Actually, why not include the context as a comment to explain the example? It's very useful and it'd just make users happy...

Yep, sounds reasonable... I will add it