[Image Banner] and [Image with text]: Add cascading fade in on scroll animation

[melissaperreault]

Summary

Add cascading fade in on scroll animation for Image banner and Image with text sections based on explorations made in #2141. Pair with UX to define the ideal strong outcome.

Details

Image banner

• Add cascading fade in on scroll
• Explore the behaviour for when the Content container visible or not. We could animate just the whole content container. Let's explore and form an opinion how it feels. When the content container is not visible, we could animate each visible content (blocks) in cascade
• Polish the transitions and delays

Image with text

*Note: Consider if we can scope in Multirow too

• Add cascading fade in on scroll
• Reveal Image first then the content in cascade.
• Explore what do we do with the content container when visible or contrasting. Is it worth cascading each line or not.

Setting

• The setting will be applied from the new Animations theme setting category. The new setting label is offered via a checkbox and its label is; Reveal sections on scroll.
• The setting will be off by default for the initial release, than turned on for the next one.