Consider updating to Vue 3.0

[NateWr]

Vue 3.0 has been released. Look into whether we can update and what breaking changes we'll need to navigate,. It is supposed to be largely compatible with 2.x, but many of the third-party dependencies we use may not yet be ready for the jump.

[NateWr]

Vue 3.0 is dropping support for IE11, but backporting many 3.0 features to Vue 2.7. It probably makes sense for us to stay on Vue 2.7 for a while longer.