Migrate to Vue.js 3

[stefandesu]

Vue.js 3 was just declared stable and has lots of improvements, especially in the performance¹, so we should consider migrating to Vue.js 3 at some point.

It makes sense to wait a little bit. In Q1 2021, Vue.js 2.7 is planned to be released and it will include many things that will make migration to 3 easier.

Here are the Vue.js 3.0 release notes: https://github.com/vuejs/vue-next/releases/tag/v3.0.0

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1: "Vue 3 has demonstrated significant performance improvements over Vue 2 in terms of bundle size (up to 41% lighter with tree-shaking), initial render (up to 55% faster), updates (up to 133% faster), and memory usage (up to 54% less)."

[stefandesu]

This should actually be higher priority now that Vue 2 is EOL: https://blog.vuejs.org/posts/vue-2-eol

However, Cocoda is a large and complex application and this will take a lot of time.