Feat: Avatars sticky positioned in timeline view

[TheWebTech]

Clear and concise description of the problem

When scrolling a timeline up toward newer posts you can’t see who wrote the post above.

Suggested solution

This was actually suggested for Ivory, but seems like something feasible to do in Elk too with position:sticky and kind of a neat experience. https://main.elk.zone/mastodon.social/@noleli/109700590302464170

https://codepen.io/noleli/full/vYaJoKw

Alternative

No response

Additional context

I'll be honest though I have a feeling some folks will prefer to have this be a toggle-able setting. I think it's probably decent enough though to be the default.

[stackblitz[bot]]

Start a new pull request in StackBlitz Codeflow.