Make sure default icons are being tree-shaken, otherwise remove them

[mattfwood]

Describe the bug
Right now, even if you use none of the default icons, they're included in your final bundle, adding a lot of bundle size.

To Reproduce
Steps to reproduce the behavior:

1. Create any react app using Minerva UI
2. Inspect final bundle
3. See icons included in final result, even if unused

Expected behavior
Unused icons should not increase final bundle size

Screenshots

[mattfwood]

For additional context, when analyzing minerva-ui using bundlephobia, almost 60% of the bundle size is from the icons.

We should probably rethink this or make it a separate package to avoid it being included unnecessarily

[mattfwood]

Also, some components (like modals and and menus) use the icons. We might need to hard-code those to be included

[mattfwood]

Update: I don't think I know how tree shaking works with TSDX. Maybe we should remove react-feather altogether.