Feature: allow passing nodeVersion as an option

[erezrokah]

As a follow up on #111 we should allow to pass nodeVersion as an option in https://github.com/netlify/framework-info/blob/master/src/main.js

See

framework-info/src/context.js

Line 26 in bd13880

const getContext = async ({ projectDir = cwd() } = {}) => {

nodeVersion is still configurable if you pass a complete context object, but that's less than ideal