fixed existing completion and added conditional completion

[tbhaxor]

Description

Fixed the vue completions

Motivation and Context

How Has This Been Tested?

Yes, by sourceing the completion file :P

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• If my change requires a change to the documentation, I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• If I have added a new file, I also added it to clean_files.txt and formatted it using lint_clean_files.sh. (wait for another PR)
• I have added tests to cover my changes, and all the new and existing tests pass.

[NoahGorny]

I never used vue before, but seems like a very clean and neat PR. Well done @tbhaxor!

I will let others take a look as well before merging, and also remind you that you are welcome to open a followup cleanup PR 😄