Set a `twaManifest.generatorApp` to `nuxt-twa`

[André Cipriani Bandarra]

This information is useful when developer have issue with their application and we can use that get details on how it's been generated. This can be added my including the code segment below here:

twaManifest.generatorApp = 'nuxt-twa';

[Nicolas Perraut]

Thanks for pointing this out!

I'll make the change ASAP unless you open a PR before

[André Cipriani Bandarra]

I'm not familiar with the stack, but hoping this is enough