Add opened .vue file to externalFiles

[doits]

Because vue file not imported from ts file are not included in project

(cherry picked from commit e4f7c8c)

---

This fixes the problem about imports not found as discussed in dense-analysis/ale#927 (comment) and following.

Without it, imports of components in .vue components always triggered a 2307: Cannot find module '@/components/Component.vue'. error.

With this change, imports now don't trigger an error anymore. Though it seems now all imports of .vue files are considered valid. E.g.:

import NotExistent from "@/components/wrongNameComponent.vue"
// no linting error even though the file does not exist

Since the project won't compile with such an error though, I think this is more acceptable to not display a linting error in this case instead of displaying wrong linting errors for existing files.

Anyway, maybe somebody with more experience can take a look at the change and maybe see why now all imports are considered valid, not only existing ones?