Support custom app.html

[agursoy]

Versions

nuxt-vite: v0.0.32
nuxt: v2.15.3

Reproduction

1- create nuxt app
2- create app.html in root directory
3- see any change applied to this file will reflect to your project
2- install vite module as described in documentation
3- app.html will be ignored

Description

If you have app.html in your nuxt project and use nuxt/vite module, this file ignored.