Support the <script setup> syntax in SFCs

[dsine-de]

Feature Request

See https://v3.vuejs.org/api/sfc-script-setup.html

Currently there are no errors with the new <script setup> syntax, but variables defined in the script are displayed (e.g. component imports, computed etc.) as dimmed when they are never read in the script itself, because you don't have to return them with this syntax and there is a tooltip <variable> is declared but its value is never read. Vetur(6133).

[zs-g]

I also encountered the same problem

[Gumper-x]

I have the same problem

[Azema4ka]

I also encountered the same problem

[lupas]

see also #2296

[SKFrozenCloud]

I also get Module '"mycomponent.vue"' has no default export.

[yoyo930021]

Duplicate of #2296