Smart link styling

[erlend-sh]

For profile-links, when a known social profile link is added we want to automatically style it with an accompanying platform logo and color (unless it’s a minimal/plain theme).

https://github.com/sethcottle/littlelink/tree/main/images/icons
https://github.com/sethcottle/littlelink/blob/main/css/brands.css

There’s likely some code overlap here with #218