Add the oauth2 keys setup in scripts/installer.js

[pkarw]

What is the motivation for adding / enhancing this feature?

Currently, we do have a fast/simple integration path with Magento2: https://github.com/DivanteLtd/vue-storefront/blob/docs/docs/guide/installation/magento.md#fast-integration

Adding the questions for the vue-storefront-api/config/local.json:magento2:api section and putting the config there in the https://github.com/DivanteLtd/vue-storefront/blob/035f3a7bc70d5669fc431fddae1caf6369682e2e/core/scripts/installer.js#L225

will be awesome!

What are the acceptance criteria

• the installer will ask the user for "url", "consumerKey", "consumerSecret", "accessToken", "accessTokenSecret"
• the installer will update the vue-storefront-api/config/local.json

[pkarw]

This section - on m2 integration - shouldn't be required. It should ask You "would You like to perform initial data import from Magento2 instance?"