Add shimmering effect to loading placeholders

[marcelvoss]

I was a bit bothered by the lack of animation during the loading phase of timelines between screens. While I think the .redacted(reason: .placeholder) option is a good choice, I think a tiny bit of shimmering makes it a bit less static and shows that something is still loading.

Preview

[Dimillian]

I'm sorry you spent time on this. I recently removed them because it cause a small performance overhead that is visible in some transition unfortunately.

[marcelvoss]

Ah, all good. Well 🤣