Use `react-icons` for icon management

[with-heart]

This project currently uses packages from @fortawesome to render icons. I'd like to propose that we replace them with react-icons for a few reasons:

• react-icons exports icons as React components, requiring less effort to use them (vs. @fortawesome which requires importing both FontAwesomeIcon and the actual icon svg and then using them together)
• react-icons provides access to icons from 21 icon sets (see the react-icons website for a searchable interface), greatly expanding the icons available for use without increasing the resulting bundle size
• since react-icons is a much more flexible solution, it's something we can standardize across our projects, allowing contributors to feel comfortable with using icons regardless of which project they're working in

Steps to implement this change:

• [ ] install react-icons packages
• [ ] replace @fortawesome imports with react-icons imports
• [ ] remove @fortawesome packages

[with-heart]

Actually from discussion in Discord it looks like we're going to be using Tabler Icons which aren't included in react-icons, so going to go ahead and close this.