Use CSS for muted-blocking animation

[danirabbit]

Fixes #137 Fixes #136

Instead of changing icon name, we transition color with CSS and add a little wiggle while we're at it

Since the current muted icon in the icon set is partial opacity, that is also preserved here. This will need to be changed in icons.

Made the transition a bit faster because:

• We have a wiggle to help it be noticeable
• It looks weird for it to linger too long if we unmute