[FR] More accurate error message for named exports in `<script setup>`

[wenfangdu]

Currently, it's "Modifiers cannot appear here." which is very general and gives the user the impression that it's not a Vue related error, I suggest changing it to something like "Named exports can't be used in <script setup>.", which is more accurate.

[wenfangdu]

It seems to be bettered handled in here.

[johnsoncodehk]

Fixed by #2582