Add ability to include icons in category names for instructions

[kiki-lee]

We can already use these icons as part of the bubbles along side the instructions. Can we also have the color formatting recognize them when we add block/categories in the instructions?

[kiki-lee]

I recognize that if we do the block discoverability work, this will be included. I'm hoping we can do this even if the rest doesn't get done.

Or, consider making the categories look more like they do in the toolbox altogether: