Add a progress bar

[txcrew]

When a user has a large "master" library with an equally massive "UI Kit" with a lot of overrides, Camilo can take up to 20 seconds to swap between brand libraries.

Is there any chance that you'd consider adding some visual feedback that Camilo is working?

Thanks!

[Pablo Sanchez Soler]

Closed because we have the native progress indicator (the color wheel)