Support Vue3

[christianlupus]

Vue 3 has been marked as the most up to date version on http://vuejs.org now some time ago.

When using this as a basis for a NC app, this package will cause problems due to the outdated vue-loader. Also the vue-template-compiler must no longer be installed as it is Vue2-only.

I have not yet successfully migrated the cookbook app from Vue 2 to Vue 3. Thus, I cannot tell if there are more issues of incompatibilities. I would in any case suggest preparing the Vue 3 migration soon. For now, I switched to a fork but I'd like to use the official repository if possible.