Upgrade to Vue 3

[KyleMaas]

Should result in a smaller bundle size. See the Performance Improvements section of:

https://github.com/vuejs/vue-next/releases/tag/v3.0.0

Looks like it should be pretty easy:

https://v3.vuejs.org/guide/migration/introduction.html

[KyleMaas]

I should note that this came up because working on another issue I ran into a problem where a library I tried to use was no longer compatible with Vue 2.x.

[KyleMaas]

Some good information here:

https://dev.to/chenxeed/awesome-breaking-changes-in-vue-3-if-you-migrate-from-vue-2-3b98

[KyleMaas]

Do we care about IE11 compatibility? Vue 3 drops that.

[KyleMaas]

nhn/tui.editor#1226

[KyleMaas]

So...maybe not quite ready yet.

[arj03]

IE11 doesn't matter, it is dead anyway. Great how you collect info in this issue.