Add loading indicators to button presses to show signs of interactivity

[paced]

It looks laggy right now, but loading indicators are more likely to show "we're currently doing something." This is good for usability.

[paced]

Font Awesome has a spinner:

<i class="fas fa-spinner fa-pulse"></i>

Clicking any element should immediately add these classes to an icon/remove the old one, and once the Promise is returned, it should replace it back with whatever the icon should have been.

[paced]

This needs to be held back for a time as we work on authentication fixes. The other v0.10.0 changes are more important for stability. Moving to v0.11.0.

[paced]

Might be some bugs with shuffle on Spotify Free as well.