[firebase-deploy] Support specifying the functions runtime engine config through firebase.json

[mark]

The firebase CLI added support for specifying the runtime engine for functions through the firebase.json instead of the package.json: https://github.com/firebase/firebase-tools/pull/2241

It appears that the firebase-deploy pipeline currently doesn't support this feature and at the moment defaults to NodeJS 12.

[Oleksandr Kyrdan]

Hi @mark

Thank you for your question!

We'll investigate this feature and notify you.

Cheers,
Oleksandr Kyrdan