Port upstream's icon changes

[ClearlyClaire]

Pitch

Commits to be ported:

• 134de73
• f08ca3f
• a4e6fe3
• fa7e64d
• e4e752c
• 7e3c10d
• 7b1d390
• 1cba91d

Motivation

Keeping up with upstream, having more modern and maintainable icons, as well as have better accessibility. This will be a lot of work, though.

[Ember-ruby]

bit sad that this would remove the animations

[ClearlyClaire]

I agree. Custom icons and animations for the “boost” icon are planned, as for the “like” icon, upstream will change it to a heart icon, so the animation would not make a lot of sense. I can probably restore the animation for the fav icon if I port those changes before it happens.