fix(vue-app): provide typescript backward compatibility

[kevinmarrec]

Types of changes

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

Description

Prevent errors like :

when using Nuxt 2.9

[kieusonlam]

Can we do one for @nuxt/config too?

[kevinmarrec]

@kieusonlam Yes !
I'm away from computer but if you or someone can make the PR it would be cool (it's juste about doing exactly same PR but around config package)

[pi0]

#6258