This allows a text button to look appropriate in the App Bar when hovering over it, while still retaining desired hover behavior elsewhere by the UX design team.

I sourced the implementation from IconButton, since the hamburger menu icon in my app was behaving as desired.

Rollup is now configured to not bundle external dependencies. This
allows Material-UI to be used in the project while not inflating
bundle sizes or causing duplicated instances of `@material-ui/styles`
from being included in an app.

All of this was to support using the default theme's box shadow for
Contained-disabled buttons.